Refactor: move some functions out of api/utils/__init__.py (#10216)

### What problem does this PR solve?

Refactor import modules.

### Type of change

- [x] Refactoring

---------

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

api/apps/__init__.py

@@ -27,7 +27,8 @@ from itsdangerous.url_safe import URLSafeTimedSerializer as Serializer
 from api.db import StatusEnum
 from api.db.db_models import close_connection
 from api.db.services import UserService
-from api.utils import CustomJSONEncoder, commands
+from api.utils.json import CustomJSONEncoder
+from api.utils import commands
 
 from flask_mail import Mail
 from flask_session import Session