create method
Implementation
Future<UPlaylist> create(String name, {List<String> paths = const <String>[]}) async {
final int now = DateTime.now().millisecondsSinceEpoch;
final UPlaylist playlist = UPlaylist(id: UUUID.uuidV4(), name: name, paths: List<String>.of(paths), createdAt: now, updatedAt: now);
_playlists.add(playlist);
await _persist();
return playlist;
}