The container for a message that is passed along the pub-sub channel that contains a Topic to define the type of message and the message itself.
This structure hold the Subscriber end of a Pub-Sub channel and can be used to create new filtered subscriber channels.
Create a topi-based pub-sub channel with a default receiver id of 1
Create Topic based Pub-Sub channel which returns the Publisher side of the channel and TopicSubscriptionFactory which can produce multiple subscribers for provided topics. The initial receiver id is required and used to label the subscribers, which makes debugging simpler.