Do not allow teams to check into a checkpoint more than once.

[ometa]

If Team X has already checked in at Checkpoint A, and subsequently left Checkpoint A to head somewhere else, then the user logged in as Checkpoint A should not see or be able to select Team X in the checkin dropdown.

[ometa]

I also notice the following odd behavior that is related.

1. Team A checks into Site Z
2. Team A's time expires, 25 mins are up. They are at zero, but they never get checked out.
3. If the user at Site Z finds Team A in the dropdown and checks them in again, the original Team A listing that's at 00:00 dissappears and is replaced with the new check in, with the countdown reset to 25:00.

Thus, we should prevent Team A from being able to be checked into a site more than once, regardless of whether or not they have checked out of that site.

[ometa]

@bppr -- I think this is the most crucial thing we can fix as there's the biggest opportunity for drunken human error.

[bppr]

Gotcha. There are few ways that we might wanna fix this, but the problem is that the countdown is global, because we use it for multiple purposes:

• can a team check in to another checkpoint? not if the countdown timer is active in redis
• how much time left does a team have at this checkpoint?

I think by saving two records, a global for the first, and then a scoped-to-checkpoint record for the second, it'll fix the problem. The other option I was thinking of is, upon a successful checkin, a team gets automatically checked out of other checkpoints.

EDIT: Cancel that. The countdown already is scoped to each checkpoint. Are we sure this is what's causing that problem? I'm going to do some testing locally to see.