Resolve "End lab sessions early"

What does this mr do?

A teacher is now able to close and open enqueueing at their own free will.

Screenshots

before

after

Student view when they can enqueue

Student view when they cannot enqueue

Teacher view when students can enqueue

Teacher view when students cannot enqueue

Does this MR meet the acceptance criteria?

• I have added a changelog entry to reflect the significant changes I made.
• Tests were created to test the feature.
• I have updated the documentation accordingly.
• I adhere to the style guide. closes #297 (closed)