Support helm chart to use a `Secret` resource to hide metadata storage db credentails.

[imcheck]

Motivation

I have tried to deploy druid using helm chart.
the helm chart doesn't support to inject environment variables related to metadata storage db credentials using Secret resource.
There's no way to inject the credentials unless using ConfigMap defined in values.yaml.

Proposed changes

• Add a way to pull some configs like db credentials (druid_metadata_storage_connector_user, druid_metadata_storage_connector_password) to each process (broker, historical, ...) from Secret resource.
• It can be custom Secret user made outside this helm chart.

Rationale

As I said on the above, it supports only to pull configs from ConfigMap.
It's hard to operate and manage values.yaml of this druid helm chart.

Operational impact

It's just add changes. so, it keeps backward compatibility.

[jwitko]

@imcheck I was able to accomplish this by adding the following to the helm chart values:

  env:
    - name: druid_metadata_storage_connector_password
      valueFrom:
        secretKeyRef:
          name: druid-pg-app
          key: password

[imcheck]

@jwitko Thank you for replying 👍 However, it seems that the druid chart (0.3.5 chart version) doesn't support it.
I also tried adding the values in values.yaml, but it didn't change anything.

[jwitko]

Sorry you are right, I forgot I was using a vendored copy of this chart that has the fixes in the above linked PR.

[asdf2014]

@imcheck @jwitko Thanks for your contribution. As mentioned in PR #15904, we have migrated the Helm Chart to a new repository, you are welcome to raise up new one there and we can maintain the Druid Helm Chart together in new repository. And this PR will closed soon. Thank you again for your understanding and collaboration.