Notification if lab busy

Summary

If waiting time of any request is > some configurable value (lab or course level), have Queue send an email. Then I can call in more TAs as needed without having to check it occasionally.

Reasoning

For ADS we have very fluctuating labs in terms of how busy it is. We have plenty of TAs, but we only schedule them as necessary. This is similar for other courses where labs are neither extremely busy (OS, CPL) nor extremely quiet (Calculus, AD).

Implementation

• If waiting time is greater than configurable value, show some warning on the edition/lab page for teachers (possibly with link to stats page to see how severe the busyness is)
• Do not send an email