[Document-URI: 2] Sync checkpoints with document identity

[karenrasmussen]

This pull request introduces support for tracking and reporting the canonical document identity (URI) for assignments, particularly to enable reliable Hide & Reveal (checkpoint) functionality. The changes ensure that the backend and frontend coordinate on the document's true identity as computed by the Hypothesis client, rather than just the launch URL. This is crucial for syncing checkpoint state and revealing assignments accurately, especially in cases where the launch URL does not uniquely identify the document in Hypothesis.

Key changes include:

Database and Model Updates

• Added a nullable document_uri column to the assignment table and model to store the canonical document identity as determined by the Hypothesis client. This value is cleared and reset if the assignment's document URL changes. [1] [2] [3]

Backend API and Service Changes

• Updated the /api/sync endpoint to accept and store the reported document_uri from the frontend, and to use this value (if present) for checkpoint syncing. The checkpoint payloads and reveal logic now consistently use document_uri instead of document_url. [1] [2] [3] [4] [5] [6]
• Added logic to prevent revealing checkpoints if the document identity has not yet been reported by the client.

Frontend/Client Coordination

• The frontend now waits for the Hypothesis client to report the document's h identity (document_uri) via RPC before syncing checkpoints. This is handled via new client-RPC infrastructure and ensures that checkpoint syncs are keyed to the correct document. [1] [2] [3] [4] [5]