Fixes: 1) Correct type hint in `validate` method of `serializers.py`; 2) Fix incorrect use of `uuid` by converting to string in various email tasks across `signals.py` and `viewsets.py`;
Extra: None;
Fixes: 1) Correct type signature in `validate` method for serializers.
Extra: 1) Remove redundant worker log format configurations in Celery; 2) Simplify log message format in log configuration for conciseness.
Fixes: 1) Adjust `mutate` methods in GraphQL mutations to support `retrieve_user` flag; 2) Ensure proper fallback to UUID handling when `retrieve_user` is set to `False`;
Extra: 1) Refactor serializers and mutations for improved customization and reduced overhead; 2) Add comments and clean up redundant code.
Fixes: 1) Remove unused `get_avatar_url` method in `UserSerializer`.
Extra: 1) Reorganize imports in serializers and middleware for clarity; 2) General code cleanup in `UserSerializer`.
