Put review updates to Slack in thread

[LFISHER7]

Review updates are currently posted to Slack as individual messages. It would be less noisy and easier to manage if review updates were posted to the relevant message notifying an issue has been created for a request

[inglesp]

This is not as easy to do as we'd like, so we're going to postpone doing this until the it looks like the volume of Slack messages risks becoming overwhelming. Please let us know when that might be!