Migrate to declarative validation: ReplicationController/scale spec.replicas field

[jpbetz]

What type of PR is this?

/kind feature

What this PR does / why we need it:

Migrates the ReplicationController's scale subresource to declarative validation.

Adds:

• +k8s:supportsSubresource (used to declare that the validation on a type also supports validation of a "status type subresource" subresource of that type)
• +k8s:isSubresource (used to declare that the validation on a type IS for a specific "scale type subresource")

Example usages:

To allow a subresource to be validated by root resource, add it as a supportedSubresource. For example, to allow the ReplicationController to validate both the scale and status subresource, use:

// +k8s:supportsSubresource=/scale
// +k8s:supportsSubresource=/status

// ReplicationController...
type ReplicationController struct { ... }

To identify a type as a subresource kind, mark it with isSubresource. For example:

// +k8s:isSubresource=/scale

// Scale ...
type Scale struct { ... }

Special notes for your reviewer:

Does this PR introduce a user-facing change?

The validation of `replicas` field in the ReplicationController `/scale` subresource has been migrated to declarative validation.
If the `DeclarativeValidation` feature gate is enabled, mismatches with existing validation are reported via metrics.
If the `DeclarativeValidationTakeover` feature gate is enabled, declarative validation is the primary source of errors for migrated fields.

/sig api-machinery

[jpbetz]

/assign @deads2k

This is best reviewed commit-by-commit. xref #130725 for how we already validate the same field on the root resource with declarative validation.

cc @thockin @aaron-prindle @yongruilin

[k8s-triage-robot]

This PR may require API review.

If so, when the changes are ready, complete the pre-review checklist and request an API review.

Status of requested reviews is tracked in the API Review project.

[aaron-prindle]

/triage approved

[k8s-ci-robot]

@aaron-prindle: The label(s) triage/approved cannot be applied, because the repository doesn't have them.

In response to this:

/triage approved

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[aaron-prindle]

/triage accepted

[jpbetz]

/test pull-kubernetes-e2e-kind-alpha-features
/test pull-kubernetes-e2e-kind-beta-features
/test pull-kubernetes-e2e-kind-alpha-beta-features

[jpbetz]

Rebased and squashed.

[jpbetz]

/retest

[thockin]

I meant to send this comment before - not sure how I missed it.

[thockin]

Thanks!

/lgtm
/approve

/hold - does @deads2k want a last look?

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 20a4262d166730b83c9df3a56e03c02b39f67514

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jpbetz, thockin

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• api/OWNERS [thockin]
• pkg/api/OWNERS [thockin]
• pkg/apis/OWNERS [thockin]
• pkg/generated/openapi/OWNERS [thockin]
• pkg/registry/core/replicationcontroller/OWNERS [thockin]
• staging/src/k8s.io/api/OWNERS [thockin]
• staging/src/k8s.io/apiextensions-apiserver/OWNERS [jpbetz,thockin]
• staging/src/k8s.io/apimachinery/pkg/OWNERS [jpbetz,thockin]
• staging/src/k8s.io/apiserver/OWNERS [jpbetz,thockin]
• staging/src/k8s.io/code-generator/OWNERS [jpbetz,thockin]

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[jpbetz]

/hold cancel

[jpbetz]

/retest