Fixes: 1) Correct `urlsafe_base64_encode` decoding logic in tests; 2) Fix queryset access issues in resolvers; 3) Address missing or incorrect imports across multiple files.
Extra: Improve code readability with consistent naming and formatting; Add `# noinspection` annotations to suppress IDE warnings; Update `pyproject.toml` to exclude `drf.py` in MyPy checks.
Replaced `fields = "__all__"` with specific fields for better control and security. Removed unused `filter_fields` to clean up the code and align with actual requirements. These changes improve maintainability and clarity.
