Require appointments to be made at least a certain number of days in advance

Make it so appointments must be made at least a certain number of days in advance. For example, if you want three days notice at least for all appointments, this feature would allow you to make it so customers can't book something less than three days in advance. So an appointment in two days could not be booked, a customer will have to pick a date that is at least three days or more into the future.