Publish the document's current main (non-branch) draft, promoting it to the published version. No request body — the draft is consumed, so the response echoes the now-published document metadata.

Only the main draft is publishable here; a branch-attached draft is published by merging its branch (POST /api/v1/models/{modelId}/branch/{branchName}/merge), so a document with no main draft returns 404. Documents that require a pull request to publish return 400.

An organization key may pass userId to act as that member: reads answer with their access, and writes are authorized and recorded as them. A user-scoped key may only name its own user (403); a user outside the organization is a 404, as is a write naming a member who has not accepted their invitation. Naming an embed user who has no live embed session is a 403. Only the operations that document userId take it — the draft-explicit …/draft/{draftIdentifier}/… routes act as the key itself.