Support multi-rack/multiregion constraints

[almazik]

Provide the ability to configure confluent.placement.constraints instead of just the number of replicas as described here:
https://docs.confluent.io/current/multi-dc-deployments/multi-region.html

The main use case for us is to be able to set up observers in a different data centre for disaster recovery purposes.

[devshawn]

Hi @almazik,

This would be interesting to implement. I'd have to understand how Confluent's kafka-topics modification with the --replica-placement flag works. Under the hood, we're just using the basic Apache Kafka AdminClient to create and manage topics.

Since it appears to just be a topic configuration set to a JSON object, you may be able to do it with our tool already. I'll have to do some investigation and see how it works. 😄