qbec validate should do a server-side dry-run

[melugoyal]

qbec validate should perform a server-side dry-run using the options provided here. this will ensure the validate step runs through admission webhooks configured on the Kubernetes API server, and make the validation more meaningful.

[gotwarlost]

@sherman-grewal - super-useful feature. Should be an opt-in and not turned on by default.

[harsimranmaan]

When implemented, this feature should be used with caution as there could be admission webhooks with side-effects. See https://kubernetes.io/docs/reference/using-api/api-concepts/#make-a-dry-run-request for details. For API servers not supporting the dry-run=server this could result in persistence. https://github.com/kubernetes/kubectl/blob/a8d3024f1144e77593d35c3f46ce4fd09c83de96/pkg/cmd/apply/apply.go#L419-L425