ECDC-3010 add support for kafka sasl auth

Created by: carez

Modification to support SASL authentication towards Kafka brokers.

The producer/consumer changes are small, but the PR is relatively big because the integration tests needed extensive changes. I tried to keep integration tests in a separate PR but in the end it was not practical.

This feature is a proof of concept to discuss changes in Kafka authentication. We do not need to merge this soon, an open discussion is highly encouraged.

See also my comment below about Kafka connection string format: https://github.com/ess-dmsc/forwarder/pull/173#discussion_r958495563