Refactor user registration (#1970)

### What problem does this PR solve?

1. Refactor error message
2. Update function name

### Type of change

- [x] Refactoring

Signed-off-by: Jin Hai <haijin.chn@gmail.com>

api/apps/user_app.py

 from api.db.services.user_service import UserService, TenantService, UserTenantService
 from api.db.services.file_service import FileService
 from api.settings import stat_logger
-from api.utils.api_utils import get_json_result, cors_reponse
+from api.utils.api_utils import get_json_result, construct_response
 
 
 @manager.route('/login', methods=['POST', 'GET'])
         user.update_date = datetime_format(datetime.now()),
         user.save()
         msg = "Welcome back!"
-        return cors_reponse(data=response_data, auth=user.get_id(), retmsg=msg)
+        return construct_response(data=response_data, auth=user.get_id(), retmsg=msg)
     else:
         return get_json_result(data=False, retcode=RetCode.AUTHENTICATION_ERROR,
                                retmsg='Email and Password do not match!')
             retmsg=f'Email: {email_address} has already registered!',
             retcode=RetCode.OPERATING_ERROR)
 
+    # Construct user info data
+    nickname = req["nickname"]
     user_dict = {
         "access_token": get_uuid(),
         "email": email_address,
-        "nickname": req["nickname"],
+        "nickname": nickname,
         "password": decrypt(req["password"]),
         "login_channel": "password",
         "last_login_time": get_format_time(),
     try:
         users = user_register(user_id, user_dict)
         if not users:
-            raise Exception('Register user failure.')
+            raise Exception(f'Fail to register {email_address}.')
         if len(users) > 1:
-            raise Exception('Same E-mail exist!')
+            raise Exception(f'Same E-mail: {email_address} exists!')
         user = users[0]
         login_user(user)
-        return cors_reponse(data=user.to_json(),
-                            auth=user.get_id(), retmsg="Welcome aboard!")
+        return construct_response(data=user.to_json(),
+                                  auth=user.get_id(),
+                                  retmsg=f"{nickname}, welcome aboard!")
     except Exception as e:
         rollback_user_registration(user_id)
         stat_logger.exception(e)
-        return get_json_result(
-            data=False, retmsg='User registration failure!', retcode=RetCode.EXCEPTION_ERROR)
+        return get_json_result(data=False,
+                               retmsg=f'User registration failure, error: {str(e)}',
+                               retcode=RetCode.EXCEPTION_ERROR)
 
 
 @manager.route("/tenant_info", methods=["GET"])

api/utils/api_utils.py

     return jsonify(response)
 
 
-def cors_reponse(retcode=RetCode.SUCCESS,
+def construct_response(retcode=RetCode.SUCCESS,
                  retmsg='success', data=None, auth=None):
     result_dict = {"retcode": retcode, "retmsg": retmsg, "data": data}
     response_dict = {}