Add tests for sorting behaviour and make album year optional (#152)

* Add tests for sorting behaviour and make album year optional

* Mark SortFeature as an interface

* Use SortOrder in Sort

* Use Dart 3 pattern destructuring in sort tests

* Make the sort expectation clearer to see in the tests

* Fix Sort.toMap

lib/localization/localization.dart

@@ -65,8 +65,6 @@ extension AppLocalizationsExtension on AppLocalizations {
             return artist;
           case SongSortFeature.album:
             return album;
-          default:
-            throw UnimplementedError();
         }
       case ContentType.album:
         switch (feature as AlbumSortFeature) {
@@ -78,8 +76,6 @@ extension AppLocalizationsExtension on AppLocalizations {
             return year;
           case AlbumSortFeature.numberOfSongs:
             return numberOfTracks;
-          default:
-            throw UnimplementedError();
         }
       case ContentType.playlist:
         switch (feature as PlaylistSortFeature) {
@@ -89,8 +85,6 @@ extension AppLocalizationsExtension on AppLocalizations {
             return dateAdded;
           case PlaylistSortFeature.name:
             return title;
-          default:
-            throw UnimplementedError();
         }
       case ContentType.artist:
         switch (feature as ArtistSortFeature) {
@@ -100,8 +94,6 @@ extension AppLocalizationsExtension on AppLocalizations {
             return numberOfAlbums;
           case ArtistSortFeature.numberOfTracks:
             return numberOfTracks;
-          default:
-            throw UnimplementedError();
         }
     }
   }

lib/logic/models/album.dart

@@ -37,20 +37,15 @@ class Album extends PersistentQueue implements PlatformAlbum {
   bool get playable => true;
 
   /// Gets album normalized year.
-  int get year {
-    return lastYear == null || lastYear! < 1000 ? clock.now().year : lastYear!;
+  int? get year {
+    return lastYear ?? firstYear;
   }
 
   /// Returns string in format `album name • year`.
   String get nameDotYear {
     return ContentUtils.appendYearWithDot(album, year);
   }
 
-  /// Returns string in format `Album • year`.
-  String albumDotName(AppLocalizations l10n) {
-    return ContentUtils.appendYearWithDot(l10n.album, year);
-  }
-
   /// Returns the album artist.
   Artist? getArtist() =>
       artistId == null ? null : ContentControl.instance.state.artists.firstWhereOrNull((el) => el.id == artistId);