Save a session back as a file

Exports the session as a `.docx` — tracked changes and all — and stores it as a new file next to the document it came from. ```json { "fileId": "msa.docx" } ``` `fileId` is the file the session was opened on, by id or by name. It must BE that file: a session that was opened on a different document answers `409 redline_file_mismatch`. The new file is named `<original>.redlined.docx` and carries `parentFileId` pointing back at it. A NAME is resolved in the org API workspace only — there is no cross-space name index. A file that lives in an explicit space must be flushed by its id. The session stays open: flush as often as you like, then let it expire or delete it. **Learn more:** [Redlining](https://docs.cloudraker.com/developers/file-tools)