stop streaming iterables

add gonic to test servers setup
gather artist image URLs on allArtists to remove weird Future<Uri> interface for artist images
move source options around

lib/sources/models.dart

@@ -19,6 +19,8 @@ abstract class SourceItem with _$SourceItem {
     required String id,
     required String name,
     DateTime? starred,
+    Uri? smallImage,
+    Uri? largeImage,
   }) = SourceArtist;
 
   @With<Starred>()