feat: add SMTP submission listener and enhance stalwart configuration

- add SMTP submission listener on port 587 with TLS requirement
- configure HAProxy frontend/backend for submission with send-proxy-v2 support
- add dynamic HAProxy node discovery for proxy trusted networks
- use service hostname instead of node FQDN for autoconfig/autodiscover
- remove redundant IMAP/IMAPS/SMTP alt-names from TLS certificates
- update VRRP CNAME configuration to use mail.main.unkin.net

modules/stalwart/templates/config.toml.epp

@@ -2,7 +2,7 @@
 # Generated by Puppet - DO NOT EDIT MANUALLY
 
 [server]
-hostname = "<%= $node_facts['networking']['fqdn'] %>"
+hostname = "<%= $service_hostname %>"
 greeting = "Stalwart ESMTP"
 
 [server.listener."smtp-relay"]
@@ -10,6 +10,14 @@ bind = ["<%= $bind_address %>:25"]
 protocol = "smtp"
 greeting = "Stalwart SMTP Relay"
 
+<% if $enable_smtp_submission { -%>
+[server.listener."submission"]
+bind = ["<%= $bind_address %>:587"]
+protocol = "smtp"
+greeting = "Stalwart SMTP Submission"
+tls.require = true
+<% } -%>
+
 <% if $enable_imap { -%>
 [server.listener."imap"]
 bind = ["<%= $bind_address %>:143"]
@@ -35,6 +43,11 @@ enable = true
 implicit = false
 certificate = "default"
 
+<% if !$haproxy_ips.empty { -%>
+[server.proxy]
+trusted-networks = ["127.0.0.0/8", "::1"<% $haproxy_ips.each |$ip| { %>, "<%= $ip %>"<% } %>]
+<% } -%>
+
 [webadmin]
 path = "<%= $webadmin_unpack_path %>"
 auto-update = <%= $webadmin_auto_update %>