Add support for defining key names used for existing SASL and TSL Secrets

[kjvellajr]

• Add support for defining key names used for existing SASL and TSL Secrets. This is useful when the existing secrets are generated from a different system, such as Strimzi.

  • Ideally the path for existingSecret should be changed to fit under the kafka.{x}.existing path, but I left it where it is currently at to not break backwards compatibility.

• Fix documentation for SASL and TSL existingSecret paths. I found that the existing documented paths kafka.sasl.credentials.existingSecret and kafka.tls.certificates.existingSecret are incorrect and instead should be kafka.sasl.existingSecret and kafka.tls.existingSecret respectively. These are used within the templates/_helpers.tpl file.

[kjvellajr]

Hello!

First off thanks for the quick response.

Generating a secret specific to Kafka-Minion is pretty easy to do and I have that scripted right now. Part of the problem I have though is keeping that secret up-to-date. If / when a new cert is issued by Strimzi I need to regenerate the Kafka-Minion secret. Anything short of a controller dedicated to creating that secret (to my knowledge) will require some manual steps which I am trying to avoid.

The last piece of the puzzle for avoiding manual steps will be annotating the deployment for Kafka-Minion to tie the deployment to the secret so that when the secret is changed, the Kafka-Minion deployment is rolled. Reloader will handle that.

If this change, and another change to support custom annotations for the Kafka-Minion deployment is out of scope, I can work on a different strategy.

Thanks for your time.

[kjvellajr]

Suggested changes have been made to the source branch.