Take into account guest's availability when rescheduling

[baileypumfleet]

If I (a Cal.com user) book another Cal.com user and they want to reschedule it on their end (instead of requesting me to reschedule), it doesn't take into account my availability and just lets them freely choose a time.

This is because the person who booked the meeting may or may not be a Cal.com user, hence we don't bother checking for their availability. But we do have the user's email, so we should look up the user and see if they're a Cal.com user, and then if so, retrieve the available times for them, and only display those when the host tries to reschedule