Comment (reason) field associated with unmanage/mute

I would like a comment field to pop up when someone tries to unmanage or mute a node. It would be nice if the NPM admin could set the field to be optional or required; and be able to edit the text indicating what to put in the field.

Reason for the request: We have some devices that have been unmanaged for a long time -- some have valid reasons which are on-going; some seem to have no reason (or the reason has expired); some were unmanaged by people who no longer work for the company. Having a comment field could assist those who follow us in understanding why a device is unmanaged or muted.