How to set custom validation on CRD using oneOf

[ffoysal]

I have a struct

type Volume struct {
	VolumeClaim string `json:"existingVolumeClaim,omitempty" yaml:"existingVolumeClaim,omitempty"`
	HostPath            string `json:"hostPath,omitempty" yaml:"hostPath,omitempty"`
}

In the CR the app should accept either VolumeClaim or HostPath not both. How to set this validation in the generated CRD. In terms functionality it will be similar to oneOf keyword

[joelanford]

@ffoysal There's currently ongoing discussion and work upstream to help with this problem. See kubernetes-sigs/controller-tools#298

Since operator-sdk relies on controller-tools for OpenAPI generation, we'll need to pursue this feature upstream.