Airlock notifier doesn't notify of rejected requests

Describe the bug
The Airlock Notifier workflow notifies the workspace team that a request has been approved, but it doesn't notify them that a request has been rejected. So if the Airlock Manager rejects a request, they are left without any indication of that unless they happen to be polling the status page.

This is undesirable, the user should be notified of the rejection, and the reviewer's reason for rejecting the request should be included.

Steps to reproduce

1. As a Workspace team member, create an airlock import or export request
2. As an Airlock Manager, reject the request
3. Wait for an email that never comes

Azure TRE release version (e.g. v0.14.0 or main):

Deployed Azure TRE components - click the (i) in the UI:

Start by tracing the Airlock Notifier workflow used after an import or export request is rejected, then compare it with the approval notification path. Confirm how the reviewer's rejection reason is stored or exposed. Done means workspace team members receive a rejection email that includes that reason, with the rejection scenario covered by an appropriate test.