Expand the fields by which the Aha/Slack integration updates Merged

There are a handful of fields that the Aha/Slack integration updates on, but in order to reduce noise on our Slack channels, a lot of our use cases center around a more contained set of criteria.

• Create/delete - you currently cannot see when POs delete records unless you select "All Fields", which updates on too many fields, creating noise.

• Custom fields - you can't update on custom fields getting populated/updated.