What is the "unsupported.do-not-use.openshift.io/override-liveness-grace-period-seconds" annotation?

Issue

• In Router Pods, the 'unsupported.do-not-use.openshift.io/override-liveness-grace-period-seconds' annotation is used:

  - apiVersion: v1
    kind: Pod
    metadata:
      annotations:
        openshift.io/scc: restricted
        unsupported.do-not-use.openshift.io/override-liveness-grace-period-seconds: "10"
  [..]
      creationTimestamp: "2021-05-11T07:36:26Z"
      generateName: router-default-7d696bbc96-
      labels:
        ingresscontroller.operator.openshift.io/deployment-ingresscontroller: default
  [..]
  

• This annotation is unexpected as it contains both "unsupported" and "do-not-use". What is the purpose of this annotation and why is it set?