MGDSTRM-9050: expose generic mechanism for injecting additional broker configuration from the operand override

[k-wall]

Using this mechanism, we can override configuration passed to the broker by populating the brokerConfig object on the operator override. This will have utility for temporary feature flags as well as experimentation in dev. Note you can remove a broker config key by passing a null value.

oc edit cm -n redhat-managed-kafka-operator  strimzi-cluster-operator.v0.26.0-15

  fleetshard_operands.yaml: |
    canary:
      init:
        image: null
    admin-server:
      image: null
    kafka:
      brokerConfig:
        kas.policy.topic-config.topic-config-policy-enforced: "true" # Inject a new broker config item
        auto.create.topics.enable: ~ # Null causes an existing one to be removed.

and showing it works end to end:

% oc logs -f kafka-instance-kafka-0 | grep kas.policy.topic-config.topic-config-policy-enforced
kas.policy.topic-config.topic-config-policy-enforced=true

[showuon]

Thanks for the feature. Overall LGTM. Left a comment. Also, I think we should put the PR description into somewhere, maybe README? wiki? Or...?

[k-wall]

Thanks for the feature. Overall LGTM. Left a comment. Also, I think we should put the PR description into somewhere, maybe README? wiki? Or...?

I added a section to ADVANCED.md

[SamBarker]

LGTM.

Happy for this to merge as is, my comments are optional.

[showuon]

Thanks for adding doc in ADVANCED.md. LGTM! Left a minor comment.

[k-wall]

@MikeEdgar any comments from you?

[MikeEdgar]

LGTM