Add kwargs parameter to extra fields methods

[dralley]

📜 Checklist

• Commits are cleanly separated with meaningful messages (simple features and bug fixes should be squashed to one commit)
• A changelog entry or entries has been added for any significant changes
• Follows the Pulp policy on AI Usage
• (For new features) - User documentation and test coverage has been added

See: Pull Request Walkthrough

[mdellweg]

Why are we doing this?

[dralley]

Because plugins call this method, and I want to make it possible to pass parameters, but right now that breaks completely and it's very coupled to versions. Allowing kwargs decouples it a bit, plugins can start passing values and it will at least be ignored instead of break.

The logic here isn't expected to be anything complex so that's fine.