Notifying staff about tickets

With notifications on, staff can also be told about tickets: when a new one is opened, and when a customer replies to an existing one. A reply on a ticket that is assigned to a particular staff member goes to that person; a new ticket, or a reply on an unassigned one, goes to every signed-in staff device. It uses the same notification setup as the customer alerts, so keys have to be generated and notifications turned on first, and each staff member still chooses per device whether to receive them. Turn it off if you would rather staff were not notified this way, for instance if you already have another alerting route.