Documents
Register a pointer-only document.
Idempotent on (user_id, source_site, provider, external_id, provider_version). Returns 201 on first registration; 200 on a re-register that matches an active row. Registration accepts storage_mode = 'pointer_only'; managed_blob and inline_small_text return 400.
post/v1/documents
Request body
Response
Idempotent re-registration; document already existed.