KEP-5883: Optional key in ConfigMapKeyRef and SecretKeyRef defaults to env var name

[dap0am]

Summary

Adds a provisional KEP for making the key field optional in configMapKeyRef
and secretKeyRef. When omitted and the EnvVarKeyDefaultsToName feature gate
is enabled, the kubelet defaults key to the enclosing env[*].name.

This eliminates boilerplate in the common case where the env var name and the
ConfigMap/Secret key are identical:

# Before
env:
  - name: DB_PASSWORD
    valueFrom:
      secretKeyRef:
        name: my-secret
        key: DB_PASSWORD  # redundant

# After (with feature gate enabled)
env:
  - name: DB_PASSWORD
    valueFrom:
      secretKeyRef:
        name: my-secret
        # key defaults to "DB_PASSWORD"

What this PR includes

• keps/sig-node/5883-optional-env-key-defaulting/kep.yaml — KEP metadata
• keps/sig-node/5883-optional-env-key-defaulting/README.md — full provisional KEP

Related

• Upstream issue: API can be streamlined: assume same key for some EnvVarSource kubernetes#132195
• Owning SIG: sig-node
• Participating SIG: sig-api-machinery
• Feature gate: EnvVarKeyDefaultsToName

/sig node
/sig api-machinery
/kind feature

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: dap0am
Once this PR has been reviewed and has the lgtm label, please assign mrunalp for approval. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Details

Needs approval from an approver in each of these files:

• keps/sig-node/OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[k8s-ci-robot]

Welcome @dap0am!

It looks like this is your first PR to kubernetes/enhancements 🎉. Please refer to our pull request process documentation to help your PR have a smooth ride to approval.

You will be prompted by a bot to use commands during the review process. Do not be afraid to follow the prompts! It is okay to experiment. Here is the bot commands documentation.

You can also check if kubernetes/enhancements has its own contribution guidelines.

You may want to refer to our testing guide if you run into trouble with your tests not passing.

If you are having difficulty getting your pull request seen, please follow the recommended escalation practices. Also, for tips and tricks in the contribution process you may want to read the Kubernetes contributor cheat sheet. We want to make sure your contribution gets all the attention it needs!

Thank you, and welcome to Kubernetes. 😃

[k8s-ci-robot]

Hi @dap0am. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work.

Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Details

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.