PIT-8968. Replaces the annotations the caller drew on this iPad (customData.PitAnnOrigin == "iOS" and customData.PitAnnDeviceId == device_id) in their personal annotation layer of this PDF, and sets the form values they filled; annotations from the web, other devices or without a device id are untouched. Idempotent: ids are kept. Only when the instance setting enable_rep_annotations_in_shared_links is on; otherwise 204 and nothing happens. 204 when everything was stored; 200 {"dropped": n} when n records could not be stored (invalid, not device-drawn, off the document's pages, or refused by the document service) and were skipped; 400 for a non-PDF or a PDF without a document; 400 when the document service refuses them for good, or 400 {"detail": "too_many_refused_annotations"} when it refuses so many that some were dropped untried; 403 for a machine token; 409 {"detail": "content_version_mismatch"} when content_version is not the file's current version (nothing written); 413 above 5 MB; 503 + Retry-After when the document service is overloaded (not one annotation could be stored) or the file's annotations are being updated.