An implementation of the IMessageHandlerAssessor interface is used to determine whether a message should be processed.
If you do not specify your own implementation of the IMessageHandlingAssessor the DefaultMessageHandlingAssessor will be used.
void RegisterAssessor(Func<PipelineEvent, bool> assessor);
void RegisterAssessor(ISpecification<PipelineEvent> specification);
Register either a function or a specification that returns true when the message should be processed; else false to ignore the message.
When the message is not processed the rest of the pipeline will still complete.