Allow booker to request a new time

[malini]

Is your feature request related to a problem? Please describe.
Say someone sends a booking request, and the appointment calendar owner accepts the request. Now the booker needs to reschedule, what can they do? Right now, nothing.

It would be nice to allow the user a propose a new meeting time instead. We have a ticket to allow them to cancel and a ticket to allow the appointment calendar owner to reschedule but we don't have a ticket to allow the booker to propose a a new time.

Describe the solution you'd like
In the booking confirmation email, we should give the booker the option to propose a new time, which upon acceptance, would remove the old appointment.