[mob][photos] Init magic cache service only if internal user (#2445)

mobile/lib/main.dart

@@ -307,7 +307,9 @@ Future<void> _init(bool isBackground, {String via = ''}) async {
       preferences,
     );
 
-    MagicCacheService.instance.init(preferences);
+    if (flagService.internalUser) {
+      MagicCacheService.instance.init(preferences);
+    }
 
     initComplete = true;
     _logger.info("Initialization done");

mobile/lib/services/magic_cache_service.dart

@@ -77,11 +77,12 @@ class MagicCacheService {
       MagicCacheService._privateConstructor();
 
   void init(SharedPreferences preferences) {
+    _logger.info("Initializing MagicCacheService");
     _prefs = preferences;
     _updateCacheIfTheTimeHasCome();
   }
 
-  Future<void> resetLastMagicCacheUpdateTime() async {
+  Future<void> _resetLastMagicCacheUpdateTime() async {
     await _prefs.setInt(
       _lastMagicCacheUpdateTime,
       DateTime.now().millisecondsSinceEpoch,
@@ -130,14 +131,14 @@ class MagicCacheService {
     try {
       _logger.info("updating magic cache");
       final magicPromptsData = await _loadMagicPrompts();
-      final magicCaches = await nonEmptyMagicResults(magicPromptsData);
+      final magicCaches = await _nonEmptyMagicResults(magicPromptsData);
       final file = File(await _getCachePath());
       if (!file.existsSync()) {
         file.createSync(recursive: true);
       }
       file.writeAsBytesSync(MagicCache.encodeListToJson(magicCaches).codeUnits);
       unawaited(
-        resetLastMagicCacheUpdateTime().onError((error, stackTrace) {
+        _resetLastMagicCacheUpdateTime().onError((error, stackTrace) {
           _logger.warning(
             "Error resetting last magic cache update time",
             error,
@@ -194,7 +195,7 @@ class MagicCacheService {
   ///Returns random non-empty magic results from magicPromptsData
   ///Length is capped at [limit], can be less than [limit] if there are not enough
   ///non-empty results
-  Future<List<MagicCache>> nonEmptyMagicResults(
+  Future<List<MagicCache>> _nonEmptyMagicResults(
     List<dynamic> magicPromptsData,
   ) async {
     //Show all magic prompts to internal users for feedback on results