Updated Proposal-upsert endpoint to handle full Authors
To match the frontend's expectation that Author creation, update, and deletion be handled through the Proposal-upsert endpoint. As a result, these operations should now work through the frontend.
Along the way:
- Added Author repo method by_user_id_and_proposal_id and related unique constraint
- Removed feature where requesting user was automatically added as an Author when creating a Proposal
Edited by Sam Kagan