Delete both the uploaded file and the thread mention. Used by
receive after a successful local import to honor forward-secrecy.
Failure to delete is fatal: the caller must NOT advance last_seen_ts
or the same blob will be re-imported (and re-logged on Slack) forever.
Delete both the uploaded file and the thread mention. Used by
receiveafter a successful local import to honor forward-secrecy. Failure to delete is fatal: the caller must NOT advancelast_seen_tsor the same blob will be re-imported (and re-logged on Slack) forever.