Fixes: 1) Correct `image_url` return logic in models; 2) Fix indentation in the `save` method of `payments` model; 3) Update a minor comment typo in `serializers.py`.
Extra: 1) Minor cleanup of unused imports in `initialize` command.
Fixes: 1) Replace generic serializers with context-specific implementations in schema definitions.
Extra: 1) Minor code cleanup and reorganization for improved readability and maintainability; 2) Add comments for new serializers.
