When accessing /booking/uid without an active session and without a cancelledBy or email parameter, display a dialog prompting for an email before showing any booking details. The entered email must match either the host or an attendee of the booking.

Why? When visiting the cancellation page via a calendar link, we can't identify who is canceling. To ensure the cancelledBy field is always set correctly, we require the email upfront.

_{From SyncLinear.com | CAL-5045}