Resolves#691
- If the broker supports native serialization, then the serialization of the
outbound payload is not done by the binder's producer binding outbound message handler.
- At the consumer binding's inbound message handler, the extraction of embedded headers
is performed only for the byte[] payload (given the deserialization would have already
occurred at the broker level)
- Add correspoinding tests in Kafka binder implementation
- Rely on the received message type to decide on using out of the box deserializer (only
if byte[] message payload is received)
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