Generate NetworkPolicy to Existing Namespaces

apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: generate-networkpolicy-existing
  annotations:
    policies.kyverno.io/title: Generate NetworkPolicy to Existing Namespaces
    policies.kyverno.io/category: Other
    policies.kyverno.io/severity: medium
    policies.kyverno.io/subject: Namespace, NetworkPolicy
    kyverno.io/kyverno-version: 1.7.0
    policies.kyverno.io/minversion: 1.7.0
    kyverno.io/kubernetes-version: "1.23"
    policies.kyverno.io/description: A NetworkPolicy is often a critical piece when provisioning new Namespaces, but there may be existing Namespaces which also need the same resource. Creating each one individually or manipulating each Namespace in order to trigger creation is additional overhead. This policy creates a new NetworkPolicy for existing Namespaces which results in a default deny behavior and labels it with created-by=kyverno.
spec:
  generateExisting: true
  rules:
    - name: generate-existing-networkpolicy
      match:
        any:
          - resources:
              kinds:
                - Namespace
      generate:
        kind: NetworkPolicy
        apiVersion: networking.k8s.io/v1
        name: default-deny
        namespace: "{{request.object.metadata.name}}"
        synchronize: true
        data:
          metadata:
            labels:
              created-by: kyverno
          spec:
            podSelector: {}
            policyTypes:
              - Egress