+kubebuilder:validation:Optional is used on types which is not supported by kubebuilder

[pmalek]

Problem statement

KIC's usage of kubebuilder core marker: +kubebuilder:validation:Optional seems to be inccorect, due to the placement of those markers.

https://book.kubebuilder.io/reference/markers/crd-validation.html mentions that +kubebuilder:validation:Optional can be used on fields and packages whereas we use that (somewhat) on types (e.g.

kubernetes-ingress-controller/pkg/apis/configuration/v1/kongclusterplugin_types.go

Line 32 in 964f9d2

// +kubebuilder:validation:Optional

)

This causes the code marker to be interpreted as imposing the validation on package level, which is undesired.

Another consequence of this is that fields in types under that package will have their Go tags understood differently: with +kubebuilder:validation:Optional, field that have json:"name" tag, will still be marked as optional in the resulting CRD.

Related Kubernetes slack thread: https://kubernetes.slack.com/archives/CAR30FCJZ/p1698841271046759

Proposed solution

Go through +kubebuilder:validation:Optional code markers in CRD types and validate if those should be relocated.

Acceptance criteria

• KIC is free of the invalid uses of +kubebuilder:validation:Optional described above (perhaps there are more ways to use it incorrectly, but the scope is just this)