Clean up domain entities: shared picture value object, lifecycle and ownership interfaces, explicit tables

backend/Core/Musify.Domain/Entities/MixItem.cs

@@ -3,25 +3,21 @@ using System.ComponentModel.DataAnnotations.Schema;
 
 namespace Musify.Domain.Entities;
 
-#pragma warning disable CS8618
 [Table("MixItems")]
 public class MixItem
 {
     [Key]
     public Guid Id { get; set; } = Guid.NewGuid();
 
-    [Required]
     public required Guid MixId { get; set; }
 
-    [Required]
-    public int Position { get; set; } = 0;
+    public int Position { get; set; }
 
-    [Required]
     public required Guid TrackId { get; set; }
 
     [ForeignKey(nameof(MixId))]
-    public Mix Mix { get; set; }
+    public Mix Mix { get; set; } = null!;
 
     [ForeignKey(nameof(TrackId))]
-    public Track Track { get; set; }
+    public Track Track { get; set; } = null!;
 }