[Feature Request]: Cool-down time for rejoining queue

[jkloosterman]

As soon as students are helped, they sometimes immediately re-add themselves to the queue. When OH are light, this means that staff need to remember not to help students they just helped, which can be especially difficult when there are multiple people handling remote OH. Add a feature that will not allow a group to re-join the queue until a certain amount of time has passed after they were last helped.