auto cancellation notifications to subadmins

Right now the only way a subadmin will receive an notification if the event that they are responsible for has been auto-cancelled is if they opt in to receive other unwanted notifications about their event (i.e. registrations and withdrawals). This all or nothing approach will end up clogging inboxes and subadmins will miss the notification that their event has been auto-cancelled due to lack of registrations. Please allow subadmins to choose which type of notification(s) they want to automatically receive.