Add post processing to the API output

[WanjiruCate]

Summary

Adds the post-processing schemas to be returned when GET /tunes/{id}

Related Issue (optional)

How to test this PR?

Make an API request to get a tune with GET /tunes/{id}

Confirm that the payload has these extra values.

  "post_processing": ....,
  "generic_processor": ...

Screenshots / Logs (optional)

Checklist

• This PR targets the main branch
• I have added or updated relevant docs.
• I have not included any secrets or credentials.
• Linting and formatting checks pass.

[WanjiruCate]

stale