Show only available dates for customers rescheduling from Customer Panel#1722

Currently, if a user accesses the Customer Panel, they’ll be able to reschedule an appointment to (what looks like) any future time. If the date is not available they’ll have to click to get a pop-up and find that out. Then guess at another date and hope that one is available.

This is a terrible user experience. Please only show available dates for users who are rescheduling. Ideally, they would see a calendar and it would be the exact same process they used to book the first time.