authentik: serve LDAP via an outpost behind the internal gateway

Adds the LDAP outpost deployment and routes ports 389 and 636 on
gateway-internal to it. 636 is a TLS listener in Terminate mode so
cert-manager renews the LDAPS certificate automatically, and both
listeners forward to the outpost's plaintext 3389.

allowedRoutes.kinds is set explicitly on both listeners: a TCP listener
permits no route kinds by default and a TLS listener defaults to
TLSRoute, so the TCPRoute would not attach otherwise.

infra/envoy-gateway/authentik/authentik-ldap-certificate.yaml

@@ -0,0 +1,14 @@
+apiVersion: cert-manager.io/v1
+kind: Certificate
+metadata:
+  name: authentik-ldap-tls
+  namespace: envoy-gateway
+spec:
+  secretName: authentik-ldap-tls
+  privateKey:
+    rotationPolicy: Always
+  issuerRef:
+    name: azure-dns
+    kind: ClusterIssuer
+  dnsNames:
+    - ldap.jsme.be

infra/envoy-gateway/authentik/authentik-ldap-gateway-patch.yaml

@@ -0,0 +1,37 @@
+# TCP listeners for the authentik LDAP outpost. kinds must be set explicitly:
+# TCP allows nothing by default and TLS defaults to TLSRoute.
+- op: add
+  path: /spec/listeners/-
+  value:
+    name: authentik-ldap
+    protocol: TCP
+    port: 389
+    allowedRoutes:
+      kinds:
+        - kind: TCPRoute
+      namespaces:
+        from: Selector
+        selector:
+          matchLabels:
+            kubernetes.io/metadata.name: authentik
+- op: add
+  path: /spec/listeners/-
+  value:
+    name: authentik-ldaps
+    protocol: TLS
+    port: 636
+    # No hostname: LDAP clients cannot be relied on to send SNI
+    tls:
+      mode: Terminate
+      certificateRefs:
+        - kind: Secret
+          name: authentik-ldap-tls
+          namespace: envoy-gateway
+    allowedRoutes:
+      kinds:
+        - kind: TCPRoute
+      namespaces:
+        from: Selector
+        selector:
+          matchLabels:
+            kubernetes.io/metadata.name: authentik

infra/envoy-gateway/kustomization.yaml

@@ -23,6 +23,7 @@ resources:
 
   # Certificates
   - authentik/authentik-certificate.yaml
+  - authentik/authentik-ldap-certificate.yaml
   - argocd/argocd-certificate.yaml
   - bentopdf/bentopdf-certificate.yaml
   - gitea/gitea-certificate.yaml
@@ -70,6 +71,12 @@ patches:
       kind: Gateway
       name: gateway-internal
     path: authentik/authentik-gateway-patch.yaml
+  - target:
+      group: gateway.networking.k8s.io
+      version: v1
+      kind: Gateway
+      name: gateway-internal
+    path: authentik/authentik-ldap-gateway-patch.yaml
   - target:
       group: gateway.networking.k8s.io
       version: v1