feat: migrate list and series seeds json endpoints to FastAPI

[harshgupta2125]

Closes #12487

refactor: This PR migrates the legacy web.py JSON endpoints for fetching and updating List and Series "seeds" to the modern FastAPI architecture.

Technical

• FastAPI Routing & Validation: Migrated all 4 route variants (/people/{user}/lists/{olid}/seeds.json, /people/{user}/series/{olid}/seeds.json, and the public equivalents) to explicit FastAPI route definitions with native 404/403 HTTP Exception handling.
• Legacy Mutator Preservation: For POST endpoints, the complex seed mutation logic is preserved by routing the safely extracted add and remove arrays directly into _LegacyListSeeds.process_seeds_update().
• Payload Handling: Utilized payload: Annotated[dict, Body(...)] to safely consume arbitrary incoming JSON without forcing strict Pydantic model evaluation on the legacy payload shape.
• Schema Output Validation: Set the GET return type hints strictly to dict (matching the legacy {"entries": [...], "size": ...} output shape) to resolve ResponseValidationError crashes during outbound serialization.
• Context & Helpers: Swapped legacy web.ctx.site dependencies for the modern site.get() in the legacy get_list_seeds fallback to prevent ThreadedDict access issues.

Testing

• Unit Testing: Verified all GET and POST routes pass via docker compose exec web python -m pytest openlibrary/tests/fastapi/ -v
• Verify GET: Navigate to http://localhost:8080/people/openlibrary/lists/OL3L/seeds.json. Verify the JSON correctly outputs the list seeds.
• Verify POST:
  1. Navigate to the interactive docs: http://localhost:8080/docs
  2. Authenticate your local session.
  3. Expand the POST /people/{username}/lists/{olid}/seeds.json endpoint.
  4. Execute a test payload (e.g., {"add": ["/works/OL123W"], "remove": []}) to verify the mutation succeeds and respects the Depends(require_authenticated_user) lock.

Screenshot

N/A - Backend API migration only.

Stakeholders

@RayBB

[Copilot]

Pull request overview

This PR migrates list/series seed JSON endpoints from legacy web.py handling into the FastAPI lists router while reusing the existing legacy seed mutation logic.

Changes:

• Adds FastAPI GET/POST routes for list and series seed JSON endpoints.
• Adds helper methods for seed lookup and update handling.
• Updates the shared legacy seed lookup helper to use the request-context site.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 5 comments.

File	Description
openlibrary/fastapi/lists.py	Adds FastAPI routes and helpers for list/series seeds GET and POST operations.
openlibrary/plugins/openlibrary/lists.py	Updates get_list_seeds to use the FastAPI-compatible request context site accessor.

[Sanket17052006]

Hey @harshgupta2125, this seems to be heading in the right direction, I haven't thoroughly tested but these are few suggestions

• You should add the deprecated decorator in the legacy endpoint
• Also a test file would be great as the other migrations follows the same pattern.

[harshgupta2125]

Hey @harshgupta2125, this seems to be heading in the right direction, I haven't thoroughly tested but these are few suggestions

• You should add the deprecated decorator in the legacy endpoint
• Also a test file would be great as the other migrations follows the same pattern.

@Sanket17052006, thanks for taking a look and for the guidance!

I've added the @deprecated("migrated to fastapi") decorator to the legacy list_seeds class in openlibrary/plugins/openlibrary/lists.py.

I also added a complete test suite in openlibrary/tests/fastapi/test_list_seeds.py covering the GET (200/404) and POST (auth/permissions) routes to match the pattern of the other migrations.

[Sanket17052006]

The deprecated decorator should be added here I don't see it though! Hope it helps :)

[harshgupta2125]

I had the file staged locally but accidentally dropped it during a git commit --amend while I was polishing up the test suite.
I just pushed a new commit that officially adds the @deprecated("migrated to fastapi")

[Sanket17052006]

Is there a reason for this here? Also the get_list_seeds is still being used in the new FastAPI endpoint. I think it would be a good idea to look at other lists migration PR, reading similar PR's helps me to get better at these migrations, hope the same for you!

[harshgupta2125]

Total typo missing the @ and putting it in the wrong spot.

You're completely right about get_list_seeds—I'm only deprecating the legacy list_seeds routing class, not the helper function since FastAPI still needs it. I've pushed the fix. Thanks for the guidance.