Describe the bug:

Cert-manager generates BadConfig events when using Gateway with non-HTTPS protocol listeners. This behavior causes frequent SYNC operations to the GatewayClass provider.

Expected behaviour:

Cert-manager should process Gateway listeners only when the protocol is set to HTTPS and silently skip HTTP listeners.

Steps to reproduce the bug:

Gateway definition:

apiVersion: gateway.networking.k8s.io/v1beta1
kind: Gateway
metadata:
  name: external-lb
  annotations:
    cert-manager.io/cluster-issuer: letsencrypt
spec:
  gatewayClassName: gke-l7-global-external-managed
  listeners:
  - name: http
    protocol: HTTP
    port: 80
  - name: https
    hostname: example.com
    protocol: HTTPS
    port: 443
    tls:
      mode: Terminate
      certificateRefs:
      - name: example-com-tls

Note: There is a HTTPS listener and also a HTTP listener to enable http-to-https redirection on the HTTPRoute side.

After applying this Gateway, the following events are frequently generated:

  Warning  BadConfig  92s (x266 over 11h)  cert-manager-gateway-shim  Skipped a listener block: [spec.listeners[0].hostname: Required value: the hostname cannot be empty, spec.listeners[0].tls: Required value: the TLS block cannot be empty]

The requirement of having a "tls" field for HTTP listeners is also not correct.

Anything else we need to know?:

Environment details::

• Kubernetes version:

Client Version: v1.27.3
Kustomize Version: v5.0.1
Server Version: v1.26.3-gke.1000

• Cloud-provider/provisioner: GKE
• cert-manager version: v1.12.2

/kind bug