[prometheus-redis-exporter] Allow REDIS_ADDR environment variable to be configured through a secret

[daconstenla]

What this PR does / why we need it

This pr adds support for (prometheus-redis-exporter)[./charts/prometheus-redis-exporter/] redis address environment variable to be configured from a secret.
It would unlock for redis address to be fetched though eg: external-secrets.

Which issue this PR fixes

There is no issue linked to this change (that I know of).

Special notes for your reviewer

I've performed some sanity checks locally to verify the chart configuration stays as is and the new configuration also works.
Since changes are all around deployment's configuration I'm using helm + yq to focus on that part of the rendered template.

This is the specific used command:

helm template . -f values.yaml |yq 'select(.kind == "Deployment").spec.template.spec.containers[0].env'

using redisAddressConfig.enabled = false

No diff, it's literally values.yaml by default, renders as:

- name: REDIS_ADDR
  value: redis://myredis:6379

using redisAddressConfig.enabled = true + redisAddressConfig.isASecret = false

 redisAddressConfig:
   # configure `REDIS_ADDR` from a configmap
-  enabled: false
+  enabled: true
   # if `true` the `REDIS_ADDR` is sourced on a secret instead of a configmap
   isASecret: false
   # Use existing configmap (ignores redisAddress)
   source:
-    name: ""
-    key: ""
+    name: "testName"
+    key: "testKey"

Renders as:

- name: REDIS_ADDR
  valueFrom:
    configMapKeyRef:
      name: testName
      key: testKey

using redisAddressConfig.enabled = true + redisAddressConfig.isASecret = true

 redisAddressConfig:
   # configure `REDIS_ADDR` from a configmap
-  enabled: false
+  enabled: true
   # if `true` the `REDIS_ADDR` is sourced on a secret instead of a configmap
-  isASecret: false
+  isASecret: true
   # Use existing configmap (ignores redisAddress)
   source:
-    name: ""
-    key: ""
+    name: "testName"
+    key: "testKey"

renders as:

- name: REDIS_ADDR
  valueFrom:
    secretKeyRef:
      name: testName
      key: testKey

Checklist

• DCO signed
• Chart Version bumped
• Title of the PR starts with chart name (e.g. [prometheus-couchdb-exporter])

[daconstenla]

@zanhsieh should I do anything else to be able to merge this change? 🙏

[zanhsieh]

@zanhsieh should I do anything else to be able to merge this change? 🙏

Nothing. Just give another maintainer @acondrat some time before I merging this.

[daconstenla]

Thank you so much for the comments @zanhsieh, good point.

Accepted the suggestions and changed the outdated comments, I hope they are good 👌.
I've also rebased to latest state of the repo.

Did again the validation of helm rendering with the combination of variables and everything seems fine.

redisAddressConfig.enabled = false

- name: REDIS_ADDR
  value: redis://myredis:6379

redisAddressConfig.enabled = true

- name: REDIS_ADDR
  valueFrom:
    configMapKeyRef:
      name: testName
      key: testKey

redisAddressConfig.enabled = true && redisAddressConfig.isSecret = true

- name: REDIS_ADDR
  valueFrom:
    secretKeyRef:
      name: testName
      key: testKey