email: Implement auto-discovery

plinth/modules/email_server/data/etc/apache2/conf-available/email-server-freedombox.conf

@@ -24,3 +24,18 @@
         TKTAuthToken "admin"
     </IfModule>
 </Location>
+
+<Location "/plinth/apps/email_server/*.xml">
+    # Require SSO
+    Include includes/freedombox-single-sign-on.conf
+    <IfModule mod_auth_pubtkt.c>
+        TKTAuthToken "admin"
+    </IfModule>
+</Location>
+
+<Location "/.well-known/autoconfig/mail/config-v1.1.xml">
+    ProxyPass http://127.0.0.1:8000/plinth/apps/email_server/config.xml
+    RequestHeader unset Cookie
+    Header unset Set-Cookie
+    Include includes/freedombox-robots.conf
+</Location>

plinth/modules/email_server/templates/config.xml

@@ -0,0 +1,22 @@
+<?xml version="1.0"?>
+<clientConfig version="1.1">
+  <emailProvider id="{{ host }}">
+    <domain>{{ host }}</domain>
+    <displayName>FreedomBox Mail</displayName>
+    <displayShortName>FBXMail</displayShortName>
+    <incomingServer type="imap">
+      <hostname>{{ host }}</hostname>
+      <port>993</port>
+      <socketType>SSL</socketType>
+      <username>%EMAILLOCALPART%</username>
+      <authentication>password-cleartext</authentication>
+    </incomingServer>
+    <outgoingServer type="smtp">
+      <hostname>{{ host }}</hostname>
+      <port>465</port>
+      <socketType>SSL</socketType>
+      <username>%EMAILLOCALPART%</username>
+      <authentication>password-cleartext</authentication>
+    </outgoingServer>
+  </emailProvider>
+</clientConfig>

plinth/modules/email_server/urls.py

@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: AGPL-3.0-or-later
 from django.urls import path
 from plinth.utils import non_admin_view
+from stronghold.decorators import public
 from . import views
 
 
@@ -13,4 +14,6 @@ urlpatterns = [
          non_admin_view(views.MyMailView.as_view()), name='my_mail'),
     path('apps/email_server/my_aliases',
          non_admin_view(views.AliasView.as_view())),
+
+    path('apps/email_server/config.xml', public(views.XmlView.as_view())),
 ]

plinth/modules/email_server/views.py

@@ -273,3 +273,18 @@ class DomainView(TabMixin, TemplateView):
                 changed[key] = value
         audit.domain.set_keys(changed)
         return self.render_to_response(self.get_context_data())
+
+
+class XmlView(TemplateView):
+    template_name = 'config.xml'
+
+    def render_to_response(self, *args, **kwargs):
+        if 200 <= kwargs.get('status', 200) < 300:
+            kwargs['content_type'] = 'text/xml; charset=utf-8'
+        response = super().render_to_response(*args, **kwargs)
+        return response
+
+    def get_context_data(self, **kwargs):
+        context = super().get_context_data(**kwargs)
+        context['host'] = self.request.get_host()
+        return context