Substitute cluster env variable

configs/certificates/certificates.yaml

@@ -0,0 +1,17 @@
+apiVersion: kustomize.toolkit.fluxcd.io/v1
+kind: Kustomization
+metadata:
+  name: certificates
+  namespace: flux-system
+spec:
+  interval: 1h
+  retryInterval: 2m
+  timeout: 5m
+  dependsOn:
+    - name: letsencrypt
+  sourceRef:
+    kind: ExternalArtifact
+    name: certificates
+  path: ./${cluster_env}
+  prune: true
+  wait: true