Side Output from a AsyncSinkBase/AsyncSinkWriter

[Aliaksandr Sazonenka]

Hi,

I have my own Sink that sends data to a HTTP endpoint and is implemented on
top of AsyncSinkBase/AsyncSinkWriter.

For non-200 responses I would like to collect request/response pairs and
send them to external storage (e.g. Kafka) for human review.

Is there a way to have a side output for AsyncSinkBase/AsyncSinkWriter?

Thanks,
-- Alex