This method returns the status of a background operation started by Update name, subject and preheader
of emails or templates, by Copy emails or templates into a folder, or by Move emails or templates into a folder.
While it runs, the status is IN_PROGRESS. Once it is COMPLETED, result lists the processed ids — updated,
copies or moved, by the operation — and every id that was not processed, with the reason. FAILED means the operation stopped
as a whole; error explains why. The status can be read within 15 minutes after the start; repeating the update is safe.