For both SMS senders and email reply to addresses this commit adds:
- a delete link
- a confirmation loop
It doesn’t let users delete:
- default SMS senders or reply to addresses (they always have to have
one)
- inbound numbers
It assumes that the API will allow updating of an attribute named
`active` on the respective database rows. It could work in a different
way. We can’t do complete deletion though because these will still be
keyed to notifications.