Backstop behavior

Describing the role of the Backstop in Hotpot.

The backstop user acts as the schedule's emergency contact. Hotpot will leverage the backstop for various situations when it cannot satisfy the on-call schedule requirements.

If the schedule cannot resolve an appropriate assignment or stint, the backstop will be considered the on-call. This is a last resort, and Hotpot will go to great lengths to squeal, squeak, and squawk at you to avoid this happening.