update persistence client test

Author: renefloor

packages/stream_chat/test/src/db/chat_persistence_client_test.dart

@@ -19,7 +19,7 @@ class TestPersistenceClient extends ChatPersistenceClient {
   bool get isConnected => throw UnimplementedError();
 
   @override
-  String? get userId => throw UnimplementedError();
+  String? get userId => 'test-user-id';
 
   @override
   Future<void> connect(String userId) => throw UnimplementedError();

packages/stream_chat_persistence/test/mock_chat_database.dart

@@ -3,6 +3,9 @@ import 'package:stream_chat_persistence/src/dao/dao.dart';
 import 'package:stream_chat_persistence/src/db/drift_chat_database.dart';
 
 class MockChatDatabase extends Mock implements DriftChatDatabase {
+  @override
+  String get userId => 'test-user-id';
+  
   @override
   UserDao get userDao => _userDao ??= MockUserDao();
   UserDao? _userDao;