A teacher can choose whether to allow late workshop submissions

1. Login as a teacher, update a workshop, tick the 'Late submissions' checkbox and set a submission deadline date in the past.
2. Switch the workshop to the submission phase.
3. Login as a student and check that you can make a submission.
4. Check that you cannot edit your submission.
5. Login as the teacher again, update the workshop and remove the submission deadline date.
6. Switch the workshop to the assessment phase.
7. Login as a different student and check that you can make a submission.
8. Check that you cannot edit your submission.