A MultiplexDestination is a transport-level endpoint capable of receiving
unsolicited incoming messages from different peers for multiple targets
identified by a unique id.
Abstract base class factoring out common Conduit logic,
allowing non-decoupled transports to be written without any
regard for the decoupled back-channel or partial response logic.
Abstract base class factoring out common Destination logic,
allowing non-decoupled transports to be written without any
regard for the decoupled back-channel or partial response logic.