[Feature] API code quality improvements

[dhruvkb]

Problem

The API server can use some refactoring and code quality improvements in a lot of places for a smoother development experience. This is a task list to collect a bunch of ways to improve code quality in the Openverse API codebase.

• 1. Using DRF generic views, viewsets and routers wherever possible instead of the lower level APIView.

🚫 2. Documenting API responses dynamically generated using serializers for ensuring they stay up to date with the actual output. (Blocked as serializers need requests in the context)

• 3. Standardising error messages and responses, ensuring 100% JSON responses even for error scenarios.
• 4. Keeping constants and magic values outside the logic and code. This helps when extending code for mode media types and functionalities.
• 5. Generate hyperlinks based on the current protocol and domain, instead of hardcoding 'https://' in some places which doesn't work for dev envs
• 6. Type hint all SerializerMethodFields so that the correct data type is shown in the Swagger API docs.

Additional context

Preferably make individual atomic PRs addressing one issue at a time, so that they can be reviewed and merged faster.

Implementation

• 🙋 I would be interested in implementing this feature.