Validate User ID, Group ID, and FS Group in CEL expressions

apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: validate-userid-groupid-fsgroup
  annotations:
    policies.kyverno.io/title: Validate User ID, Group ID, and FS Group in CEL expressions
    policies.kyverno.io/category: Sample in CEL
    policies.kyverno.io/severity: medium
    policies.kyverno.io/subject: Pod
    policies.kyverno.io/minversion: 1.11.0
    kyverno.io/kyverno-version: 1.11.0
    kyverno.io/kubernetes-version: 1.26-1.27
    policies.kyverno.io/description: All processes inside a Pod can be made to run with specific user and groupID by setting `runAsUser` and `runAsGroup` respectively. `fsGroup` can be specified to make sure any file created in the volume will have the specified groupID. This policy validates that these fields are set to the defined values.
spec:
  validationFailureAction: Audit
  background: true
  rules:
    - name: validate-userid-groupid-fsgroup
      match:
        any:
          - resources:
              kinds:
                - Pod
              operations:
                - CREATE
                - UPDATE
      validate:
        cel:
          expressions:
            - expression: object.spec.?securityContext.?runAsUser.orValue(1) == 1000
              message: User ID should be 1000.
            - expression: object.spec.?securityContext.?runAsGroup.orValue(1) == 3000
              message: Group ID should be 3000.
            - expression: object.spec.?securityContext.?fsGroup.orValue(1) == 2000
              message: fs Group should be 2000.