Constraints have detailed behavioral descriptions (that need to be in the text) defined in class EiConstraintBehavior.
Consider whether a similar set for EiOpt (out) is appropriate.
There are race conditions (and incorrect logic) that could deliver an EiEvent when a VTN is opted out. What should the VTN do? Apply its own opt out schedule and ignore? Or consider whether to execute the event?
Closed with rewrite of EiOptType and EiAvailType.