Cancel a Parents' Evening appointment

Requires permissions: Guardian or Parent or ParentsEvening or Student

Only the family it belongs to (the parent it was booked for, whether they or their child booked it, or their partner), or an administrator, may cancel. With notify, the server tells the teacher, and the family too when an administrator cancels; recipients and wording are the server's (FR-023). The teacher is not told while families are still booking: they cannot see their bookings until both windows have closed.