Add shared pagination, projections and ownership helpers; simplify query and command handlers

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

@@ -2,8 +2,8 @@ using ErrorOr;
 using Mediator;
 using Microsoft.EntityFrameworkCore;
 using Musify.Application.Contracts;
+using Musify.Application.Shared;
 using Musify.Application.Tracks.Responses;
-using Musify.Domain.ValueObjects;
 
 namespace Musify.Application.Tracks;
 
@@ -15,16 +15,15 @@ public class GetTrackByIdQueryHandler(IDatabase database)
 {
     public async ValueTask<ErrorOr<TrackApplicationResponse>> Handle(GetTrackByIdQuery request, CancellationToken cancellationToken)
     {
-        var entity = await database.Tracks.AsNoTracking()
-            .Include(t => t.Owner)
-            .Include(t => t.Tags)
-            .Where(t => t.Id == request.TrackId && t.LifeCycleStatus == LifeCycleStatus.Active)
-            .Select(t => new { Track = t, ListensCount = t.ListeningHistories.Count(l => l.IsCounted) })
+        var track = await database.Tracks
+            .AsNoTracking()
+            .Active()
+            .Where(t => t.Id == request.TrackId)
+            .SelectResponse()
             .SingleOrDefaultAsync(cancellationToken);
 
-        if (entity == null)
-            return Error.NotFound();
-
-        return TrackApplicationResponse.FromEntity(entity.Track, entity.ListensCount);
+        return track == null
+            ? AppErrors.NotFound("Track", request.TrackId)
+            : track;
     }
 }