Secure internal and external cluster communication

When running Kafka in public cloud, but often also in private cloud, it is essential to secure all Kafka interface and all Kafka communication.

We should secure (authentication / authorization) both the internal communication withion the Kafka cluster (Kafka-Kafka, Zookeeper-Zookeeper and Kafka-Zookeeper), comunication between Kafka cluster and our own tools (Topic controller, Cluster controller) as well as add support for securing user communication (Kaycloak authentication).

Secure should ideally mean Encryption, Authentication and Authorization.

This Epic should be broker down into tasks.

User stories:

• As a Administrator, I want to manage users (create, edit, delete) so that the applications don't use Kafka anonymously
• As a Administrator, Assign credentials to Kafka clients to make it possible for applications to connect using the credentials