kafka header not mirroring

**Is your feature request related to a problem? Please describe.**
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I try to [Mirroring kafka clusters](https://github.com/linkedin/brooklin/wiki/Mirroring-Kafka-Clusters).
and I using same as tutorial.
but brooklin miss mirroring that kafka headers.

**Describe the solution you'd like**
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kafka header also mirroring it.

**Describe alternatives you've considered**
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I checked "KafkaMirrorMakerConnectorTask.java".
I think add kafka header copy logic in `translate` method.

**Additional context**
Add any other context about the feature request here.

Start with KafkaMirrorMakerConnectorTask.java and inspect the translate method, following the Mirroring Kafka Clusters tutorial linked in the issue. Trace how records are translated and determine where headers are currently omitted. Done means mirrored records retain their Kafka headers when using the documented mirroring setup.

Written by the indexing model from the issue text.