Ability to add optional message when denying a request

[bobokun]

Is your feature request related to a problem? Please describe.
No

Describe the solution you'd like
A way to add a optional message when declining a request that will be passed to the notification to the end user so they know the reason for declining the request.

Describe alternatives you've considered
Sending a message to the end user telling them why their request got declined

[modem7]

This would also tie in with #572

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[bobokun]

No please stale bot :(

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.