Kafka async producer does not handle traces correctly

[mantzas]

Is your feature request related to a problem? Please describe

When sending a message via async producer the span is not properly handled.

Is this a bug? Please provide steps to reproduce, a failing test etc.

Yes, since we mark a span either succeeded or failed based when sending the message.

Describe the solution

Async producer provides channels for success and failures that need to be monitored. Beware the documentation. Check the Metadata field of the Producer message to pass the span produced.