backend/Core/Musify.Application/Albums/AddTrackToAlbum.cs

@@ -20,7 +20,7 @@ namespace Musify.Application.Albums
             var album = await database.Albums
                 .AsNoTracking()
                 .SingleOrDefaultAsync(a => a.Id == request.AlbumId, cancellationToken);
-            if (album is null)
+            if (album == null)
             {
                 logger.LogInformation("Album {AlbumId} not found", request.AlbumId);
                 return Error.NotFound();
@@ -35,7 +35,7 @@ namespace Musify.Application.Albums
             var track = await database.Tracks
                 .AsNoTracking()
                 .SingleOrDefaultAsync(t => t.Id == request.TrackId, cancellationToken);
-            if (track is null)
+            if (track == null)
             {
                 logger.LogInformation("Track {TrackId} not found", request.TrackId);
                 return Error.NotFound(description: $"Track {request.TrackId} not found");

backend/Core/Musify.Application/Albums/DeleteAlbum.cs

@@ -18,7 +18,7 @@ namespace Musify.Application.Albums
         {
             var album = await database.Albums
                 .SingleOrDefaultAsync(a => a.Id == request.AlbumId, cancellationToken);
-            if (album is null)
+            if (album == null)
             {
                 logger.LogDebug("Album {AlbumId} not found", request.AlbumId);
                 return Error.NotFound();

backend/Core/Musify.Application/Albums/GetAlbumById.cs

@@ -29,7 +29,7 @@ namespace Musify.Application.Albums
                 })
                 .SingleOrDefaultAsync(cancellationToken);
 
-            if (album is null)
+            if (album == null)
                 return Error.NotFound();
 
             return AlbumApplicationResponse.FromEntity(album.Album, album.TrackCount, album.CoverTrackIds);

backend/Core/Musify.Application/Albums/GetAlbumCover.cs

@@ -25,7 +25,7 @@ namespace Musify.Application.Albums
                 .Select(a => a.Pictures)
                 .SingleOrDefaultAsync(cancellationToken);
 
-            if (pictures is null)
+            if (pictures == null)
                 return Error.NotFound();
 
             var routes = albumConfiguration.Routes;

backend/Core/Musify.Application/Albums/RemoveTrackFromAlbum.cs

@@ -19,7 +19,7 @@ namespace Musify.Application.Albums
             var album = await database.Albums
                 .AsNoTracking()
                 .SingleOrDefaultAsync(a => a.Id == request.AlbumId, cancellationToken);
-            if (album is null)
+            if (album == null)
             {
                 logger.LogInformation("Album {AlbumId} not found", request.AlbumId);
                 return Error.NotFound();
@@ -37,7 +37,7 @@ namespace Musify.Application.Albums
                 .ToListAsync(cancellationToken);
 
             var link = albumTracks.SingleOrDefault(albumTrack => albumTrack.TrackId == request.TrackId);
-            if (link is null)
+            if (link == null)
             {
                 logger.LogInformation("Track {TrackId} not in album {AlbumId}", request.TrackId, request.AlbumId);
                 return Error.NotFound(description: "Track is not in the album.");

backend/Core/Musify.Application/Albums/UpdateAlbum.cs

@@ -36,7 +36,7 @@ namespace Musify.Application.Albums
         {
             var album = await database.Albums
                 .SingleOrDefaultAsync(a => a.Id == request.AlbumId, cancellationToken);
-            if (album is null)
+            if (album == null)
             {
                 logger.LogInformation("Album {AlbumId} not found", request.AlbumId);
                 return Error.NotFound();

backend/Core/Musify.Application/Likes/ToggleTrackLike.cs

@@ -30,7 +30,7 @@ namespace Musify.Application.Likes
                 .SingleOrDefaultAsync(like => like.UserId == request.UserId && like.TrackId == request.TrackId, cancellationToken);
 
             bool nowLiked;
-            if (existingLike is not null)
+            if (existingLike != null)
             {
                 database.TrackLikes.Remove(existingLike);
                 nowLiked = false;

backend/Core/Musify.Application/Mixes/GetMixById.cs

@@ -19,7 +19,7 @@ namespace Musify.Application.Mixes
                 .Include(mix => mix.Items)
                 .SingleOrDefaultAsync(mix => mix.Id == request.MixId && mix.UserId == request.UserId, cancellationToken);
 
-            if (mix is null)
+            if (mix == null)
                 return Error.NotFound(description: $"Mix {request.MixId} was not found");
 
             var orderedItems = mix.Items.OrderBy(item => item.Position).ToList();

backend/Core/Musify.Application/PlayLists/AddTrackToPlayList.cs

@@ -19,7 +19,7 @@ namespace Musify.Application.PlayLists
         {
             var playList = await database.PlayLists
                 .SingleOrDefaultAsync(pl => pl.Id == request.PlayListId, cancellationToken);
-            if (playList is null)
+            if (playList == null)
             {
                 logger.LogInformation("Playlist {PlayListId} not found", request.PlayListId);
                 return Error.NotFound();

backend/Core/Musify.Application/PlayLists/DeletePlayList.cs

@@ -20,7 +20,7 @@ namespace Musify.Application.PlayLists
         public async ValueTask<ErrorOr<Success>> Handle(DeletePlayListCommand request, CancellationToken cancellationToken)
         {
             var playList = await database.PlayLists.SingleOrDefaultAsync(p => p.Id == request.PlayListId, cancellationToken);
-            if (playList is null)
+            if (playList == null)
             {
                 logger.LogDebug("Playlist {PlayListId} not found", request.PlayListId);
                 return Error.NotFound();

backend/Core/Musify.Application/PlayLists/GetPlayListById.cs

@@ -29,7 +29,7 @@ namespace Musify.Application.PlayLists
                 })
                 .SingleOrDefaultAsync(cancellationToken);
 
-            if (entry is null)
+            if (entry == null)
                 return Error.NotFound();
 
             if (entry.PlayList.Visibility == PlaylistVisibility.Private

backend/Core/Musify.Application/PlayLists/GetPlayListCover.cs

@@ -25,7 +25,7 @@ namespace Musify.Application.PlayLists
                 .Select(p => p.Pictures)
                 .SingleOrDefaultAsync(cancellationToken);
 
-            if (pictures is null)
+            if (pictures == null)
                 return Error.NotFound();
 
             var routes = playListConfiguration.Routes;

backend/Core/Musify.Application/PlayLists/RemoveTrackFromPlayList.cs

@@ -18,7 +18,7 @@ namespace Musify.Application.PlayLists
         {
             var playList = await database.PlayLists
                 .SingleOrDefaultAsync(pl => pl.Id == request.PlayListId, cancellationToken);
-            if (playList is null)
+            if (playList == null)
             {
                 logger.LogInformation("Playlist {PlayListId} not found", request.PlayListId);
                 return Error.NotFound();
@@ -32,7 +32,7 @@ namespace Musify.Application.PlayLists
 
             var link = await database.PlayListHasTracks
                 .SingleOrDefaultAsync(plt => plt.PlayListId == request.PlayListId && plt.TrackId == request.TrackId, cancellationToken);
-            if (link is null)
+            if (link == null)
             {
                 logger.LogInformation("Track {TrackId} not in playlist {PlayListId}", request.TrackId, request.PlayListId);
                 return Error.NotFound(description: "Track is not in the playlist.");

backend/Core/Musify.Application/PlayLists/UpdatePlayList.cs

@@ -35,7 +35,7 @@ namespace Musify.Application.PlayLists
         public async ValueTask<ErrorOr<PlayListApplicationResponse>> Handle(UpdatePlayListCommand request, CancellationToken cancellationToken)
         {
             var playListEntity = await database.PlayLists.SingleOrDefaultAsync(pl => pl.Id == request.PlayListId, cancellationToken);
-            if (playListEntity is null)
+            if (playListEntity == null)
             {
                 logger.LogInformation("Playlist {PlayListId} not found", request.PlayListId);
                 return Error.NotFound();

backend/Core/Musify.Application/Services/TrackStreamIssuer.cs

@@ -32,7 +32,7 @@ public sealed class TrackStreamIssuer(
 
         // Anonymous listeners have no User row to satisfy ListeningHistory's foreign key against, and
         // their plays aren't "history" anyone can look back on anyway, so there's nothing to record.
-        if (userId is not null)
+        if (userId != null)
         {
             var newListeningHistory = new ListeningHistory
             {
@@ -48,7 +48,7 @@ public sealed class TrackStreamIssuer(
 
     private long? AnonymousFragmentBytes(long? userId)
     {
-        if (userId is not null || playbackConfiguration.AnonymousFragmentSeconds <= 0)
+        if (userId != null || playbackConfiguration.AnonymousFragmentSeconds <= 0)
             return null;
 
         return (long)playbackConfiguration.AnonymousFragmentSeconds * playbackConfiguration.EstimatedAudioBytesPerSecond;

backend/Core/Musify.Application/Services/UploadIntentValidator.cs

@@ -42,7 +42,7 @@ public sealed class UploadIntentValidator(
         var intent = await database.UploadIntents
             .FirstOrDefaultAsync(i => i.Id == intentId, cancellationToken);
 
-        if (intent is null || intent.UserId != userId)
+        if (intent == null || intent.UserId != userId)
             return Error.NotFound(description: "Upload intent not found or not accessible.");
 
         if (intent.IsConsumed)
@@ -52,7 +52,7 @@ public sealed class UploadIntentValidator(
             return Error.Validation(description: "Upload intent has expired.");
 
         var metadata = await storageService.HeadObjectAsync(intent.Bucket, intent.Key, cancellationToken);
-        if (metadata is null)
+        if (metadata == null)
             return Error.NotFound(description: "Uploaded object not found in storage. Upload the file first.");
 
         if (metadata.ContentLength > config.MaxUploadBytes)

backend/Core/Musify.Application/Tracks/CreateTrack.cs

@@ -35,7 +35,7 @@ namespace Musify.Application.Tracks
         {
             var user = await database.Users
                 .SingleOrDefaultAsync(u => u.Id == request.UserId, cancellationToken);
-            if (user is null)
+            if (user == null)
             {
                 logger.LogWarning("User {UserId} not found", request.UserId);
                 return Error.NotFound(description: $"User {request.UserId} not found");

backend/Core/Musify.Application/Tracks/DeleteTrack.cs

@@ -23,7 +23,7 @@ namespace Musify.Application.Tracks
         public async ValueTask<ErrorOr<Success>> Handle(DeleteTrackCommand request, CancellationToken cancellationToken)
         {
             var track = await database.Tracks.SingleOrDefaultAsync(t => t.Id == request.TrackId, cancellationToken);
-            if (track is null)
+            if (track == null)
             {
                 logger.LogInformation("Track {TrackId} not found", request.TrackId);
                 return Error.NotFound();

backend/Core/Musify.Application/Tracks/GetTrackById.cs

@@ -21,7 +21,7 @@ namespace Musify.Application.Tracks
                 .Select(t => new { Track = t, ListensCount = t.ListeningHistories.Count })
                 .SingleOrDefaultAsync(cancellationToken);
 
-            if (entity is null)
+            if (entity == null)
                 return Error.NotFound();
 
             return TrackApplicationResponse.FromEntity(entity.Track, entity.ListensCount);

backend/Core/Musify.Application/Tracks/GetTrackStream.cs

@@ -23,7 +23,7 @@ namespace Musify.Application.Tracks
     {
         public async ValueTask<ErrorOr<TrackStreamResponse>> Handle(GetTrackStreamQuery request, CancellationToken cancellationToken)
         {
-            if (request.UserId is null && !playbackConfiguration.AllowAnonymousListening)
+            if (request.UserId == null && !playbackConfiguration.AllowAnonymousListening)
                 return Error.Unauthorized(description: "Sign in to stream music, or ask an administrator to enable anonymous listening.");
 
             var track = await database.Tracks.AsNoTracking()

backend/Core/Musify.Application/Users/GetUserById.cs

@@ -20,7 +20,7 @@ namespace Musify.Application.Users
                 .Select(u => UserApplicationResponse.FromEntity(u))
                 .SingleOrDefaultAsync(cancellationToken);
 
-            if (user is null)
+            if (user == null)
                 return Error.NotFound();
 
             return user;

backend/Core/Musify.Application/Users/GetUserProfile.cs

@@ -38,7 +38,7 @@ namespace Musify.Application.Users
                 })
                 .SingleOrDefaultAsync(cancellationToken);
 
-            if (user is null)
+            if (user == null)
                 return Error.NotFound();
 
             var followersCount = await database.UserFollows

backend/Core/Musify.Application/Users/SyncUser.cs

@@ -23,7 +23,7 @@ namespace Musify.Application.Users
             var user = await database.Users
                 .SingleOrDefaultAsync(u => u.Id == request.Id, cancellationToken);
 
-            if (user is null)
+            if (user == null)
             {
                 await database.Users.AddAsync(new User
                 {

backend/Core/Musify.Application/Users/UnfollowUser.cs

@@ -18,7 +18,7 @@ namespace Musify.Application.Users
             var follow = await database.UserFollows
                 .SingleOrDefaultAsync(f => f.FollowerId == request.FollowerId && f.FollowedId == request.FollowedId, cancellationToken);
 
-            if (follow is null)
+            if (follow == null)
                 return new Success();
 
             database.UserFollows.Remove(follow);

backend/Core/Musify.Infrastructure/MassTransit/Activities/Albums/MarkAlbumAsFailedActivity.cs

@@ -19,7 +19,7 @@ namespace Musify.Infrastructure.MassTransit.Activities.Albums
             var album = await database.Albums
                 .SingleOrDefaultAsync(a => a.Id == executeContext.Arguments.AlbumId, executeContext.CancellationToken);
 
-            if (album is not null)
+            if (album != null)
             {
                 album.LifeCycleStatus = LifeCycleStatus.Failed;
                 await database.SaveChangesAsync(executeContext.CancellationToken);

backend/Core/Musify.Infrastructure/MassTransit/Activities/Audio/UpdateTrackAudioActivity.cs

@@ -93,7 +93,7 @@ namespace Musify.Infrastructure.MassTransit.Activities.Audio
             try
             {
                 var track = await database.Tracks.SingleOrDefaultAsync(t => t.Id == compensateContext.Log.TrackId, compensateContext.CancellationToken);
-                if (track is null)
+                if (track == null)
                     throw new InvalidOperationException($"Track with id {compensateContext.Log.TrackId} not found");
 
                 track.Audio.FolderName = compensateContext.Log.PreviousAudioFolderName;

backend/Core/Musify.Infrastructure/MassTransit/Activities/Pictures/UpdateAlbumPictureActivity.cs

@@ -31,14 +31,14 @@ namespace Musify.Infrastructure.MassTransit.Activities.Pictures
                     [executeContext.Arguments.AlbumId],
                     cancellationToken: executeContext.CancellationToken);
 
-                if (album is null)
+                if (album == null)
                 {
                     logger.LogWarning("Album {AlbumId} not found",
                         executeContext.Arguments.AlbumId);
                     throw new InvalidOperationException($"Album with id {executeContext.Arguments.AlbumId} not found");
                 }
 
-                if (album.Pictures is null)
+                if (album.Pictures == null)
                 {
                     logger.LogWarning("Album {AlbumId} has no pending picture upload",
                         executeContext.Arguments.AlbumId);
@@ -85,7 +85,7 @@ namespace Musify.Infrastructure.MassTransit.Activities.Pictures
                     [compensateContext.Log.AlbumId],
                     cancellationToken: compensateContext.CancellationToken);
 
-                if (album is null)
+                if (album == null)
                 {
                     return compensateContext.Compensated();
                 }

backend/Core/Musify.Infrastructure/MassTransit/Activities/Pictures/UpdatePlayListPictureActivity.cs

@@ -31,14 +31,14 @@ namespace Musify.Infrastructure.MassTransit.Activities.Pictures
                     [executeContext.Arguments.PlayListId],
                     cancellationToken: executeContext.CancellationToken);
 
-                if (playList is null)
+                if (playList == null)
                 {
                     logger.LogWarning("Playlist {PlayListId} not found",
                         executeContext.Arguments.PlayListId);
                     throw new InvalidOperationException($"PlayList with id {executeContext.Arguments.PlayListId} not found");
                 }
 
-                if (playList.Pictures is null)
+                if (playList.Pictures == null)
                 {
                     logger.LogWarning("Playlist {PlayListId} has no pending picture upload",
                         executeContext.Arguments.PlayListId);
@@ -85,7 +85,7 @@ namespace Musify.Infrastructure.MassTransit.Activities.Pictures
                     [compensateContext.Log.PlayListId],
                     cancellationToken: compensateContext.CancellationToken);
 
-                if (playList is null)
+                if (playList == null)
                 {
                     return compensateContext.Compensated();
                 }

backend/Core/Musify.Infrastructure/MassTransit/Activities/Pictures/UpdateTrackPictureActivity.cs

@@ -31,7 +31,7 @@ namespace Musify.Infrastructure.MassTransit.Activities.Pictures
                     [executeContext.Arguments.TrackId],
                     cancellationToken: executeContext.CancellationToken);
 
-                if (track is null)
+                if (track == null)
                 {
                     logger.LogWarning("Track {TrackId} not found",
                         executeContext.Arguments.TrackId);
@@ -79,7 +79,7 @@ namespace Musify.Infrastructure.MassTransit.Activities.Pictures
                     [compensateContext.Log.TrackId],
                     cancellationToken: compensateContext.CancellationToken);
 
-                if (track is null)
+                if (track == null)
                     return compensateContext.Compensated();
 
                 track.Pictures.OriginalName = compensateContext.Log.PreviousOriginalPictureKey;

backend/Core/Musify.Infrastructure/MassTransit/Activities/PlayLists/DeletePlayListFromDbActivity.cs

@@ -18,7 +18,7 @@ namespace Musify.Infrastructure.MassTransit.Activities.PlayLists
             var playList = await database.PlayLists
                 .SingleOrDefaultAsync(p => p.Id == executeContext.Arguments.PlayListId, executeContext.CancellationToken);
 
-            if (playList is null)
+            if (playList == null)
             {
                 logger.LogInformation(
                     "PlayList {PlayListId} not found while deleting from DB, skipping",

backend/Core/Musify.Infrastructure/MassTransit/Activities/PlayLists/MarkPlayListAsFailedActivity.cs

@@ -19,7 +19,7 @@ namespace Musify.Infrastructure.MassTransit.Activities.PlayLists
             var playList = await database.PlayLists
                 .SingleOrDefaultAsync(p => p.Id == executeContext.Arguments.PlayListId, executeContext.CancellationToken);
 
-            if (playList is not null)
+            if (playList != null)
             {
                 playList.LifeCycleStatus = LifeCycleStatus.Failed;
                 await database.SaveChangesAsync(executeContext.CancellationToken);

backend/Core/Musify.Infrastructure/MassTransit/Activities/PlayLists/MarkPlayListAsRemovingActivity.cs

@@ -19,7 +19,7 @@ namespace Musify.Infrastructure.MassTransit.Activities.PlayLists
             var playList = await database.PlayLists
                 .SingleOrDefaultAsync(p => p.Id == executeContext.Arguments.PlayListId, executeContext.CancellationToken);
 
-            if (playList is null)
+            if (playList == null)
             {
                 logger.LogInformation(
                     "PlayList {PlayListId} not found while marking as removing, skipping",

backend/Core/Musify.Infrastructure/MassTransit/Activities/Tracks/DeleteTrackFromDbActivity.cs

@@ -18,7 +18,7 @@ namespace Musify.Infrastructure.MassTransit.Activities.Tracks
             var track = await database.Tracks
                 .SingleOrDefaultAsync(t => t.Id == executeContext.Arguments.TrackId, executeContext.CancellationToken);
 
-            if (track is null)
+            if (track == null)
             {
                 logger.LogInformation(
                     "Track {TrackId} not found while deleting from DB, skipping",

backend/Core/Musify.Infrastructure/MassTransit/Activities/Tracks/MarkTrackAsFailedActivity.cs

@@ -19,7 +19,7 @@ namespace Musify.Infrastructure.MassTransit.Activities.Tracks
             var track = await database.Tracks
                 .SingleOrDefaultAsync(t => t.Id == executeContext.Arguments.TrackId, executeContext.CancellationToken);
 
-            if (track is not null)
+            if (track != null)
             {
                 track.LifeCycleStatus = LifeCycleStatus.Failed;
                 await database.SaveChangesAsync(executeContext.CancellationToken);

backend/Core/Musify.Infrastructure/MassTransit/Activities/Tracks/MarkTrackAsRemovingActivity.cs

@@ -19,7 +19,7 @@ namespace Musify.Infrastructure.MassTransit.Activities.Tracks
             var track = await database.Tracks
                 .SingleOrDefaultAsync(t => t.Id == executeContext.Arguments.TrackId, executeContext.CancellationToken);
 
-            if (track is null)
+            if (track == null)
             {
                 logger.LogInformation(
                     "Track {TrackId} not found while marking as removing, skipping",

backend/Core/Musify.Infrastructure/MassTransit/RoutingSlip/Builders/DeletePlayListRoutingSlipBuilder.cs

@@ -37,7 +37,7 @@ namespace Musify.Infrastructure.MassTransit.RoutingSlip.Builders
                 EndpointHelper.BuildExecuteActivityUri(MarkPlayListAsRemovingActivity.ExecuteEndpointName),
                 new MarkPlayListAsRemovingArguments(playListId));
 
-            if (playList?.Pictures is not null)
+            if (playList?.Pictures != null)
             {
                 var bucket = storageConfiguration.Bucket;
                 var routes = playListConfiguration.Routes;

backend/Core/Musify.Infrastructure/MassTransit/RoutingSlip/Builders/DeleteTrackRoutingSlipBuilder.cs

@@ -37,7 +37,7 @@ namespace Musify.Infrastructure.MassTransit.RoutingSlip.Builders
                 EndpointHelper.BuildExecuteActivityUri(MarkTrackAsRemovingActivity.ExecuteEndpointName),
                 new MarkTrackAsRemovingArguments(trackId));
 
-            if (track is not null)
+            if (track != null)
             {
                 var bucket = storageConfiguration.Bucket;
 

backend/Core/Musify.Infrastructure/Persistence/AuditableEntityInterceptor.cs

@@ -21,7 +21,7 @@ namespace Musify.Infrastructure.Persistence
 
         private static void ApplyTimestamps(DbContext? context)
         {
-            if (context is null)
+            if (context == null)
                 return;
 
             // SavingChanges(Async) fires before EF's own automatic change detection for this

backend/Core/Musify.Infrastructure/Services/SingleFlightCache.cs

@@ -16,7 +16,7 @@ namespace Musify.Infrastructure.Services
             if (duration <= TimeSpan.Zero)
                 return await factory();
 
-            if (cache.TryGetValue(key, out TValue? cached) && cached is not null)
+            if (cache.TryGetValue(key, out TValue? cached) && cached != null)
                 return cached;
 
             var pending = (Lazy<Task<ErrorOr<TValue>>>)inFlight.GetOrAdd(

backend/Core/Musify.Infrastructure/Services/StorageService.cs

@@ -276,7 +276,7 @@ namespace Musify.Infrastructure.Services
             {
                 listResponse = await amazonS3.ListObjectsV2Async(listRequest, cancellationToken);
 
-                if (listResponse.S3Objects is null or { Count: 0 } )
+                if (listResponse.S3Objects == null|| listResponse.S3Objects.Count == 0)
                     break;
 
                 var deleteRequest = new DeleteObjectsRequest
@@ -289,9 +289,6 @@ namespace Musify.Infrastructure.Services
 
                 var deleteResponse = await amazonS3.DeleteObjectsAsync(deleteRequest, cancellationToken);
 
-                // Some S3-compatible backends (SeaweedFS included) omit the <Error> list from the
-                // XML response entirely when nothing failed, which the SDK deserializes as null
-                // rather than an empty list — real AWS S3 always returns a (possibly empty) list.
                 var deleteErrors = deleteResponse.DeleteErrors ?? [];
                 if (deleteErrors.Count > 0)
                 {

backend/Core/Musify.Infrastructure/Services/StreamTicketService.cs

@@ -29,9 +29,9 @@ namespace Musify.Infrastructure.Services
             var now = DateTimeOffset.UtcNow;
 
             var claims = new Dictionary<string, object> { ["prefix"] = keyPrefix };
-            if (userId is not null)
+            if (userId != null)
                 claims["sub"] = userId.Value.ToString();
-            if (maxBytes is not null)
+            if (maxBytes != null)
                 claims["maxBytes"] = maxBytes.Value.ToString();
 
             var descriptor = new SecurityTokenDescriptor

backend/Directory.Packages.props

@@ -29,8 +29,9 @@
     <PackageVersion Include="Microsoft.Extensions.Options.ConfigurationExtensions" Version="10.0.12" />
     <PackageVersion Include="Microsoft.Extensions.Options.DataAnnotations" Version="10.0.12" />
     <PackageVersion Include="Microsoft.IdentityModel.JsonWebTokens" Version="8.23.0" />
-    <PackageVersion Include="Microsoft.OpenApi" Version="3.10.2" />
+    <PackageVersion Include="Microsoft.OpenApi" Version="2.12.2" />
     <PackageVersion Include="MimeMapping" Version="4.0.0" />
+    <PackageVersion Include="Newtonsoft.Json" Version="13.0.4" />
     <PackageVersion Include="Npgsql.EntityFrameworkCore.PostgreSQL" Version="10.0.3" />
     <PackageVersion Include="OpenTelemetry" Version="1.19.0" />
     <PackageVersion Include="OpenTelemetry.Api" Version="1.19.0" />
@@ -43,7 +44,7 @@
     <PackageVersion Include="OpenTelemetry.Instrumentation.Process" Version="1.15.1-beta.1" />
     <PackageVersion Include="OpenTelemetry.Instrumentation.Runtime" Version="1.19.0" />
     <PackageVersion Include="Scalar.AspNetCore" Version="2.17.6" />
-    <PackageVersion Include="SixLabors.ImageSharp" Version="4.1.2" />
+    <PackageVersion Include="SixLabors.ImageSharp" Version="2.1.13" />
     <PackageVersion Include="X.PagedList" Version="10.6.0" />
     <PackageVersion Include="X.PagedList.EF" Version="10.6.0" />
     <PackageVersion Include="Yarp.ReverseProxy" Version="2.3.0" />

backend/Hosts/Musify.Api/Api.csproj

@@ -19,6 +19,7 @@
     <PackageReference Include="Microsoft.EntityFrameworkCore" />
     <PackageReference Include="Microsoft.EntityFrameworkCore.Relational" />
     <PackageReference Include="Microsoft.OpenApi" />
+    <PackageReference Include="Newtonsoft.Json" />
     <PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL" />
     <PackageReference Include="OpenTelemetry" />
     <PackageReference Include="OpenTelemetry.Api" />

backend/Hosts/Musify.Api/Authentication/JwtBearerEventsHandler.cs

@@ -125,7 +125,7 @@ public sealed class JwtBearerEventsHandler(
 
     public override Task Challenge(JwtBearerChallengeContext context)
     {
-        if (context.AuthenticateFailure is not null)
+        if (context.AuthenticateFailure != null)
             logger.LogWarning("JWT challenge: {Error} - {Description}", context.Error, context.ErrorDescription);
         return Task.CompletedTask;
     }

backend/Hosts/Musify.Api/Filters/ValidationFilter.cs

@@ -8,7 +8,7 @@ public sealed class ValidationFilter<T>(IValidator<T> validator) : IEndpointFilt
     {
         var argument = context.Arguments.OfType<T>().FirstOrDefault();
 
-        if (argument is null)
+        if (argument == null)
             return await next(context);
 
         var result = await validator.ValidateAsync(argument, context.HttpContext.RequestAborted);

backend/Hosts/Musify.Api/Validators/PlayLists/UpdatePlayListRequestValidator.cs

@@ -10,10 +10,10 @@ public sealed class UpdatePlayListRequestValidator : AbstractValidator<UpdatePla
         RuleFor(x => x.NewName)
             .NotEmpty()
             .MaximumLength(50)
-            .When(x => x.NewName is not null);
+            .When(x => x.NewName != null);
 
         RuleFor(x => x.NewDescription)
             .MaximumLength(256)
-            .When(x => x.NewDescription is not null);
+            .When(x => x.NewDescription != null);
     }
 }

backend/Hosts/Musify.Worker/Worker.csproj

@@ -15,6 +15,7 @@
     <PackageReference Include="Microsoft.Extensions.Hosting" />
     <PackageReference Include="Microsoft.Extensions.Options.DataAnnotations" />
     <PackageReference Include="MimeMapping" />
+    <PackageReference Include="Newtonsoft.Json" />
     <PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL" />
     <PackageReference Include="SixLabors.ImageSharp" />
   </ItemGroup>

backend/Tests/Musify.Api.Tests/Api.Tests.csproj

@@ -11,6 +11,7 @@
   <ItemGroup>
     <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" />
+    <PackageReference Include="Newtonsoft.Json" />
     <PackageReference Include="NSubstitute" />
     <PackageReference Include="Testcontainers.PostgreSql" />
     <PackageReference Include="xunit.v3" />

backend/Tests/Musify.Application.Tests/Albums/CreateAlbumCommandHandlerTests.cs

@@ -47,7 +47,7 @@ namespace Musify.Application.Tests.Albums
             var stored = await Database.Albums.FindAsync([result.Value.Id], TestContext.Current.CancellationToken);
             Assert.NotNull(stored);
             Assert.Equal("MY ALBUM", stored.NormalizedTitle);
-            Assert.Equal("cover.webp", stored.Pictures.OriginalName);
+            Assert.Equal("cover.webp", stored.Pictures?.OriginalName);
             await eventBus.Received(1).PublishAsync(Arg.Any<Musify.Application.Events.CreateAlbumResourcesEvent>(), Arg.Any<CancellationToken>());
         }
 

backend/Tests/Musify.Application.Tests/Albums/UpdateAlbumCommandHandlerTests.cs

@@ -62,7 +62,7 @@ namespace Musify.Application.Tests.Albums
             Assert.False(result.IsError);
             var stored = await Database.Albums.FindAsync([album.Id], TestContext.Current.CancellationToken);
             Assert.NotNull(stored);
-            Assert.Equal("new-cover.webp", stored.Pictures.OriginalName);
+            Assert.Equal("new-cover.webp", stored.Pictures?.OriginalName);
             await eventBus.Received(1).PublishAsync(Arg.Any<Musify.Application.Events.UpdateAlbumPictureSourceEvent>(), Arg.Any<CancellationToken>());
         }
 

backend/Tests/Musify.Application.Tests/PlayLists/CreatePlayListCommandHandlerTests.cs

@@ -56,7 +56,7 @@ namespace Musify.Application.Tests.PlayLists
             Assert.False(result.IsError);
             var stored = await Database.PlayLists.FindAsync([result.Value.Id], TestContext.Current.CancellationToken);
             Assert.NotNull(stored);
-            Assert.Equal("cover.webp", stored.Pictures.OriginalName);
+            Assert.Equal("cover.webp", stored.Pictures?.OriginalName);
             await eventBus.Received(1).PublishAsync(Arg.Any<Musify.Application.Events.CreatePlayListResourcesEvent>(), Arg.Any<CancellationToken>());
         }
 

backend/Tests/Musify.Infrastructure.Tests/Infrastructure.Tests.csproj

@@ -14,6 +14,7 @@
          solution (and Musify.Infrastructure itself) is built against. -->
     <PackageReference Include="Microsoft.EntityFrameworkCore.Relational" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" />
+    <PackageReference Include="Newtonsoft.Json" />
     <PackageReference Include="NSubstitute" />
     <PackageReference Include="Testcontainers" />
     <PackageReference Include="Testcontainers.PostgreSql" />

backend/Tests/Musify.StreamingGateway.Tests/Authentication/TicketValidatorTests.cs

@@ -36,7 +36,7 @@ namespace Musify.StreamingGateway.Tests.Authentication
             DateTime? expires = null, DateTime? notBefore = null, long? maxBytes = null)
         {
             var claims = new Dictionary<string, object> { ["prefix"] = prefix };
-            if (maxBytes is not null)
+            if (maxBytes != null)
                 claims["maxBytes"] = maxBytes.Value.ToString();
 
             var descriptor = new SecurityTokenDescriptor

backend/Tests/Musify.StreamingGateway.Tests/Middleware/TicketValidationMiddlewareTests.cs

@@ -39,7 +39,7 @@ namespace Musify.StreamingGateway.Tests.Middleware
         private string IssueValidToken(string prefix = Prefix, long? maxBytes = null)
         {
             var claims = new Dictionary<string, object> { ["prefix"] = prefix };
-            if (maxBytes is not null)
+            if (maxBytes != null)
                 claims["maxBytes"] = maxBytes.Value.ToString();
 
             return new JsonWebTokenHandler().CreateToken(new SecurityTokenDescriptor