Separate responsibilities: start-listening command, API-side JSON converters, bulk track endpoints, mix kinds

backend/Tests/Musify.Application.Tests/TestSupport/TestDatabase.cs

@@ -143,8 +143,6 @@ public sealed class TestDatabase : DbContext, IDatabase
 
     public DbSet<Track> Tracks => Set<Track>();
 
-    public DbSet<UserHasTrack> UserHasTracks => Set<UserHasTrack>();
-
     public DbSet<PlayListHasTrack> PlayListHasTracks => Set<PlayListHasTrack>();
 
     public DbSet<Mix> Mixes => Set<Mix>();

backend/Tests/Musify.Application.Tests/TestSupport/TestEntities.cs

@@ -154,14 +154,12 @@ public static class TestEntities
 
     public static Mix Mix(
         long userId,
-        string title = "Test Mix",
-        string? subtitle = null,
+        MixKind kind = MixKind.Discovery,
         int position = 0) =>
         new()
         {
             UserId = userId,
-            Title = title,
-            Subtitle = subtitle,
+            Kind = kind,
             Position = position
         };