Bulk-delete chat sessions

Starts an asynchronous job that soft-deletes up to 100 chat rooms. The Location resource is polled until completed or failed; a completed job may contain individual failed results, including not_found for a malformed target ID. If the job itself fails, the target it stopped on carries delete_failed and every target behind it carries not_attempted, which means it was left untouched and is safe to resubmit.