feat: manage haproxy for stalwart (#420)

- add frontends for imap, imaps and smtp
- add backends for webadmin, imap, imaps and smtp

Reviewed-on: #420

hieradata/roles/infra/halb/haproxy2.yaml

@@ -163,6 +163,39 @@ profiles::haproxy::frontends:
         - 'set-header X-Forwarded-Proto https'
         - 'set-header X-Real-IP %[src]'
         - 'use-service prometheus-exporter if { path /metrics }'
+  fe_imap:
+    description: 'Frontend for Stalwart IMAP (STARTTLS)'
+    bind:
+      0.0.0.0:143: []
+    mode: 'tcp'
+    options:
+      log: global
+      default_backend: be_stalwart_imap
+      tcp-request:
+        - inspect-delay 5s
+        - content accept if { req_len 0 }
+  fe_imaps:
+    description: 'Frontend for Stalwart IMAPS (implicit TLS)'
+    bind:
+      0.0.0.0:993: []
+    mode: 'tcp'
+    options:
+      log: global
+      default_backend: be_stalwart_imaps
+      tcp-request:
+        - inspect-delay 5s
+        - content accept if { req_len 0 }
+  fe_smtp:
+    description: 'Frontend for Stalwart SMTP'
+    bind:
+      0.0.0.0:25: []
+    mode: 'tcp'
+    options:
+      log: global
+      default_backend: be_stalwart_smtp
+      tcp-request:
+        - inspect-delay 5s
+        - content accept if { req_len 0 }
 
 profiles::haproxy::backends:
   be_letsencrypt: