RC1 of Strimzi Operators 0.21.0

Jakub Scholz

Release Candidate 1 of Strimzi Operators 0.21.0 is now available for testing with a lot of changes and improvements. The main changes since the 0.20.0 release include:
* Add support for declarative management of connector plugins in Kafka Connect CR
* Add `inter.broker.protocol.version` to the default configuration in example YAMLs
* Add support for `secretPrefix` property for User Operator to prefix all secret names created from KafkaUser resource.
* Allow configuring labels and annotations for Cluster CA certificate secrets
* Add the JAAS configuration string in the sasl.jaas.config property to the generated secrets for KafkaUser with SCRAM-SHA-512 authentication.
* Strimzi `test-container` has been renamed to `strimzi-test-container` to make the name more clear
* Updated the CPU usage metric in the Kafka, ZooKeeper and Cruise Control dashboards to include the CPU kernel time (other than the current user time)
* Allow disabling ownerReference on CA secrets
* Make it possible to run Strimzi operators and operands with read-only root filesystem
* Move from Docker Hub to Quay.io as our container registry
* Add possibility to configure DeploymentStrategy for Kafka Connect, Kafka Mirror Maker (1 and 2), and Kafka Bridge
* Support passing metrics configuration as an external ConfigMap
* Enable CORS configuration for Cruise Control
* Add support for rolling individual Kafka or ZooKeeper pods through the Cluster Operator using an annotation
* Add support for Topology Spread Constraints in Pod templates
* Make Kafka `cluster-id` (KIP-78) available on Kafka CRD status

There are also some deprecations and removals which you should be aware of:
* The `metrics` field in the Strimzi custom resources has been deprecated and will be removed in the future. For configuring metrics, use the new `metricsConfig` field and pass the configuration via ConfigMap.

This version of Strimzi supports Kubernetes 1.16 and higher.

Any feedback can be provided on the Strimzi mailing list, on the #strimzi Slack channel on CNCF Slack or as a GitHub issue.

Thanks & Regards
Jakub & Strimzi team