`stopping-definition` to stop when causality is broken.

Causality is a property of the simulation model stating that a future event cannot change what has been done in the past already, so all changes in the state should not contradict any past event.

In practise, we check the `next-snapshot` `date` is equal or after the current `snapshot`.

`stopping-definition` to stop when the execution of an event is not found in the registry.

`stopping-definition` to stop when an execution has raised an exception.

`stopping-definition` to stop when no future events exists anymore.

built-in `stopping-definition` can create `stopping-cause` but they are not accessible for modellers, they are hard coded.

Stops when the request is not valid.

Stops when the response is not valid.