Over Sign Up / Overfilling of shifts occuring when volunteers click "submit" on the same shifts at the same time.

Bloomerang uses a "cart" system for volunteers to add shifts. Bloomerang also allows us to set a "signup limit" to shifts to not have too many volunteers pick up them same shift.

The signup limit is not being respected, as we often see over sign up / overfilling of shifts. When the shifts sit in the volunteers cart, it allows them to click "submit" on a full shift if it wasn't full when they added it to their cart (and it allows multiple volunteers to do so, meaning we've have a shift overfill by upwards of 10 volunteers for a shift that had a signup limit of 1).

Bloomerang should do a final check of the signup limit before allowing a volunteer to add a full shift to their schedule. The history/timestamp shows that the system knows when they hit submit, but doesn't respect the limit. When it does a final check of the limit and a shift is full, Bloomerang should show an error/bring them back to refresh the shifts to only show open ones instead.