TF-1289: [Data] implement storeSubscription in fcm repository

lib/features/push_notification/data/model/fcm_subscription.dart

@@ -0,0 +1,23 @@
+
+import 'package:equatable/equatable.dart';
+import 'package:hive/hive.dart';
+import 'package:tmail_ui_user/features/caching/utils/caching_constants.dart';
+
+part 'fcm_subscription.g.dart';
+
+@HiveType(typeId: CachingConstants.FCM_SUBSCRIPTION_HIVE_CACHE_INDENTITY)
+class FCMSubscriptionCache extends HiveObject with EquatableMixin {
+
+  static const String keyCacheValue = 'fcmSubscriptionCache';
+  
+  @HiveField(0)
+  final String deviceId;
+
+  @HiveField(1)
+  final String subscriptionId;
+
+  FCMSubscriptionCache(this.deviceId, this.subscriptionId);
+
+  @override
+  List<Object?> get props => [deviceId, subscriptionId];
+}