fix: remove required from entities' id

also adds "Global" entity for storing global configuration

Data/ApplicationDbContext.cs

@@ -17,6 +17,7 @@ public class ApplicationDbContext : DbContext
 	public DbSet<Artist> Artists => Set<Artist>();
 	public DbSet<Genre> Genres => Set<Genre>();
 	public DbSet<GenreSong> GenreSongs => Set<GenreSong>();
+	public DbSet<Global> Globals => Set<Global>();
 	public DbSet<Image> Images => Set<Image>();
 	public DbSet<Playlist> Playlists => Set<Playlist>();
 	public DbSet<PlaylistSong> PlaylistSongs => Set<PlaylistSong>();
@@ -52,6 +53,9 @@ public class ApplicationDbContext : DbContext
 		builder.Entity<Genre>(g => {
 			g.HasIndex(g => g.NormalizedName).IsUnique();
 		});
+		builder.Entity<Global>(c => {
+			c.HasIndex(c => c.Key).IsUnique();
+		});
 		builder.Entity<Playlist>(p => {
 			p.HasIndex(p => p.Uri).IsUnique();
 		});