Lecturer schould be able to un-queue students after accepting a queue request

TODO

• Check if teacher has buttons after accepting a request and fix if not

Summary

After a student booked a slot and the booking was approved, the booking should still be cancellable by the student (i think it is?), AND also the lecturer.

Reasoning

We used the Queue to schedule oral exams. Some students got wet feet last minute, and sent a cancellation email to us. I would now want to cancel their appointment. But I cannot (?). So I need to send them a mail and tell them to please un-queue themselves?

To fix

Reject button does not always show up for teachers