KafkaAcknowledgedMessage lacks headers

[blindspotbounty]

We use kafka headers to store technical information about message.
However, it was surprising that there are no headers in KafkaAcknowledgedMessage.

Could you advise whether there are plans to add it at some point, please?

[FranzBusch]

I think we can easily add this. We just need to parse the headers out of the underlying rd message pointer. Feel free to open a PR.