setLocale method

Implementation

@override
Future<Either<Failure, void>> setLocale(String locale) async {
  try {
    await _isar.writeTxn(() async {
      final existing = await _isar.appPreferencesDtos.get(_prefsId);
      final dto = existing ?? (await _paramsFromDefaults());
      dto.locale = locale;
      await _isar.appPreferencesDtos.put(dto);
    });
    return const Right(null);
  } catch (e) {
    return Left(CacheFailure("Failed to set locale: $e"));
  }
}