EitherProcessor takes in an event and allows each listener the option to modify and return via Left or respond with an alternate response with Right (immediately stops propagating and returns).
InterceptProcessor gives each listener the ability to Stop or Continue the processing.
ListProcessor expects an Option[R] from each listener and builds a list from Some[R] responses.
ModifiableProcessor takes in an event and allows each listener the option to modify and return
ModifiableProcessor takes in a value and allows each listener the option to replace the value as it goes through the process finally returning the result.
OptionProcessor gives each listener the ability to return Option[R].
TokenProcessor works similarly to UnitProcessor except there is no real "event" that is supplied so EventToken is provided.
UnitProcessor takes in E and passes it to all listeners.