save method
Implementation
@override
Future<void> save(AppSettings settings) async {
await ensureConfigFile(_settingsPath);
final file = File(_settingsPath);
final content = await file.readAsString();
await file.writeAsString(
mergeSettingsScalars(
content,
themeName: settings.themeName,
lastSelectedDeviceId: settings.lastSelectedDeviceId,
),
);
}