Auto Release

[meffmadd]

Is your feature request related to a problem? Please describe.
Instructors who do exams with the grader want to automatically release assignments when the exam starts and not have to do it manually.

Describe the solution you'd like
In the normal release workflow timeline, the "Release" button gets a second option, "Timed Release", which opens a pop-up where a release date can be set. The assignment then has a new status - "release-scheduled" - and the date is recorded in the assignment settings dict.

In the grader-service there is a polling function that checks all assignments with the "release-scheduled" status and releases the assignment when the release date is reached. The status becomes "released" and the release date is deleted from the settings.