Allow Issues to have both priority, and terminally.
This allows an issue to expire automatically when it is past it's due-date; forcing an action to reopen and extend it's life.
It probably shouldn't expire and auto-close them within Pagure itself. But we could have a state that indicates it's past due or something.
We already have custom fields which can be set as Dates.
I'm not sure if we want to do more on this