Perm on ExamType Endpoint / ExamType Subscription

Prior:

The ExamType Endpoint was only accessible to Reviewers. Tutors could create ExamType subscriptions but had no way of knowing what query key's are available.

Now:

Endpoint has perm TutorOrReviewer. Tutors can see available exams and create corresponding subscriptions.

Problem:

Biases concerning different fields of study might influence a tutors grading.

Proposed Solutions:

1. Tutors don't have access to the exam endpoint and can't create exam subscriptions (only reviewers can)
2. Tutors don't have access to the endpoint and exam subscriptions are not possible
3. Tutors don't have access to the endpoint and we implement the following subscription behavior:
   • tutors can create random and subtype subscriptions
   • reviewers can create all kinds of subscriptions (including exam type)
   • reviewers can assign subscriptions to tutors (as long as no constraints are violated)
   • when tutors have active sub type/exam type/student subscriptions (only possible via assignment from reviewer) they only receive information about assignments (current, next, etc.) but not about the query key or type
   • this allows the reviewer to assign specific work tot tutors without exposing to much information