feat: Ability to set SANs to the API server certificate

[maksym-iv]

In some cases, if apiServerAddress is modified (which is highly not recommended for sure, and should be done if implications are clear) it may be needed to se custom SANs. Example use-case:

• Temporary AWS instance with the ephemeral pub IP
• Kind cluster set up in that AWS instance
• apiServerAddress is set to the internal EC2 IP
• External CI system communicates with the temporary Kind cluster
• Error Unable to connect to the server: tls: failed to verify certificate: x509: certificate is valid for 10.96.0.1, 172.18.0.2, 0.0.0.0, not 18.118.189.168

Fixes #3755

[linux-foundation-easycla]

• ✅login: maksym-iv / (54efec6)

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[k8s-ci-robot]

Hi @maksym-iv. Thanks for your PR.

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[BenTheElder]

Hi, our process is to discuss the approach to features first and agree to the feature and an approach before reviewing code that we will have to maintain.

This is covered in our contributor guide: https://kind.sigs.k8s.io/docs/contributing/getting-started/

[maksym-iv]

Hi, our process is to discuss the approach to features first and agree to the feature and an approach before reviewing code that we will have to maintain.

This is covered in our contributor guide: https://kind.sigs.k8s.io/docs/contributing/getting-started/

Sure, my bad. I've created the issue before PR and opened a PR just to demonstrate the potential approach, can close the PR.
And yep, my bad, I somehow missed the

Please file an enhancement / feature request issue to discuss features before filing a PR

[aojea]

So, you can already do this with kubeadm patches https://kind.sigs.k8s.io/docs/user/configuration/#kubeadm-config-patches

kind: Cluster
apiVersion: kind.x-k8s.io/v1alpha4
kubeadmConfigPatchesJSON6902:
- group: kubeadm.k8s.io
  version: v1beta2
  kind: ClusterConfiguration
  patch: |
    - op: add
      path: /apiServer/certSANs/-
      value: 172.16.0.2
networking:
  apiServerAddress: "0.0.0.0"
  apiServerPort: 6443

this is just exposing this through the kind API, but for the end user is just 1 line of yaml vs 8 lines of yaml, and will conflict with existing solution of using patches

[maksym-iv]

this is just exposing this through the kind API, but for the end user is just 1 line of yaml vs 8 lines of yaml, and will conflict with existing solution of using patches

Sure, makes sense, closing than. Thanks for clarification

[BenTheElder]

Thank you!