Add ability to limit which employees can confirm a sales appointment

We require the ability to limit which employees can confirm a sales appointment. They must not be able to self confirm. By requiring a manager to confirm the appointment we can better hold the team accountable as to the legitimacy of their appointments, improve the likelihood of the appointment showing and increase manager awareness of when the customer arrives by having the client ask for the manager confirming the call.

Self confirmed appointments don't show up as often as a manager confirmed call. More shows equals more sales.