Actions should be able to mark task as auto cancel

Much like auto approve, there are cases where an action should mark itself (and the task) as auto cancelling. This is because there are cases where the task is entirely invalid, and the user simply cannot or should not update it and try again but rather submit a new one. These should be automatically cancelled so that we have less unfinished tasks sitting around in the invalid state.

There should also be an optional cancel email notification.