envoy-gateway: add seerr-test.jsme.be listener + cert (OIDC preview test)

Temporary listener/cert for the seerr-test instance running the
preview-new-oidc build. Remove along with the seerr-test workload when
testing is done.

envoy-gateway/kustomization.yaml

@@ -22,6 +22,7 @@ resources:
   - it-tools/certificate.yaml
   - jellyfin/certificate.yaml
   - seerr/certificate.yaml
+  - seerr/test-certificate.yaml
   - jenkins/certificate.yaml
   - longhorn/certificate.yaml
   - monitoring/certificate.yaml
@@ -92,6 +93,12 @@ patches:
       kind: Gateway
       name: gateway-internal
     path: seerr/gateway-patch.yaml
+  - target:
+      group: gateway.networking.k8s.io
+      version: v1
+      kind: Gateway
+      name: gateway-internal
+    path: seerr/test-gateway-patch.yaml
   - target:
       group: gateway.networking.k8s.io
       version: v1