feat:增加服务器接口模块

lib/apis/user_api.dart

@@ -0,0 +1,10 @@
+import 'package:sweet_chat_app/models/user.dart';
+import 'package:sweet_chat_app/services/dio_service.dart';
+
+Future<List<User>> getUserFriendsApi(int userId) async {
+  final res = await dioService.get('/user/friend/$userId');
+
+  if (res.data == null) return [];
+
+  return (res.data as List).map((e) => User.fromJson(e)).toList();
+}