🌱 enable requiredfields linter

[v47]

What type of PR is this?

/kind cleanup

What this PR does / why we need it:

• Enables Kube API linter’s requiredfields check to ensure required API fields aren’t omitted or pointer types.
• Removes omitempty tags from required OIDC identity provider fields and MachinePool block device DeviceName fields to align with new linter rules and guarantee proper serialization.

Which issue(s) this PR fixes :
Fixes #5492

Checklist:

• squashed commits
• includes documentation
• includes emoji in title
• adds unit tests
• adds or updates e2e tests

Release note:

Enabled requiredfields Kube API linter check and removed `omitempty` tags from required EKS and experimental MachinePool API fields.

[k8s-ci-robot]

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[k8s-ci-robot]

Hi @v47. Thanks for your PR.

I'm waiting for a kubernetes-sigs 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.

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[fiunchinho]

/ok-to-test

[JoelSpeed]

Please update KAL to the latest version. After discussion with the Kube API reviewers, and updates to the Kube API conventions, the required fields rule has been rewritten and will now recommend omitempty on fields, so this PR is going in the opposite direction to the current best advice

[damdo]

/hold

[richardcase]

Also the PR needs a retitle.

[JoelSpeed]

In a lot of cases, changing the serialization can be breaking, though clients do need to update to the new library version for this to take effect.

Where we already have a non-zero min length, adding omitempty/omitzero should be safe, since no one should have persisted an empty value anyway

Where there aren't min lengths already, this could be problematic. Have you checked what the behaviour is when a zero value is persisted and you upgrade into this schema/client?

Existing values should be fine because of ratcheting validation, but, if the client now starts omitting the value, it will remove the value on write and this will lead to a required validation coming up, which would then be breaking

[JoelSpeed]

Have you verified that this ratchets?

[JoelSpeed]

Might be better to use a CEL validation if possible, isURL likely more comprehensive

[v47]

Did you have something like this in mind?

// +kubebuilder:validation:XValidation:rule="isURL(self) && url(self).getScheme() == 'https'"

[JoelSpeed]

Exactly, and then you can add ,message="..." with a custom error message too