refactor: app metadata

mobile/lib/infrastructure/entities/metadata.entity.dart

@@ -0,0 +1,18 @@
+import 'package:drift/drift.dart';
+import 'package:immich_mobile/infrastructure/utils/drift_default.mixin.dart';
+
+class MetadataEntity extends Table with DriftDefaultsMixin {
+  const MetadataEntity();
+
+  TextColumn get key => text()();
+
+  TextColumn get value => text()();
+
+  DateTimeColumn get updatedAt => dateTime().withDefault(currentDateAndTime)();
+
+  @override
+  Set<Column> get primaryKey => {key};
+
+  @override
+  String get tableName => "metadata";
+}