upload new photos in background with a service (#382)

* properly done background backup service

* new concurrency/locking management with heartbeat

fix communication erros with Kotlin plugin on start/stop service methods

better error handling for BackgroundService public methods

Add default notification message when service is running

* configurable WiFi & charging requirement for service

* use translations in background service

mobile/lib/modules/backup/background_service/localization.dart

@@ -0,0 +1,27 @@
+import 'package:flutter/foundation.dart';
+import 'package:easy_localization/src/asset_loader.dart';
+import 'package:easy_localization/src/easy_localization_controller.dart';
+import 'package:easy_localization/src/localization.dart';
+import 'package:immich_mobile/constants/locales.dart';
+
+/// Workaround to manually load translations in another Isolate
+Future<bool> loadTranslations() async {
+  await EasyLocalizationController.initEasyLocation();
+
+  final controller = EasyLocalizationController(
+    supportedLocales: locales,
+    useFallbackTranslations: true,
+    saveLocale: true,
+    assetLoader: const RootBundleAssetLoader(),
+    path: translationsPath,
+    useOnlyLangCode: false,
+    onLoadError: (e) => debugPrint(e.toString()),
+    fallbackLocale: locales.first,
+  );
+
+  await controller.loadTranslations();
+
+  return Localization.load(controller.locale,
+      translations: controller.translations,
+      fallbackTranslations: controller.fallbackTranslations);
+}