[Nginx][Web] Client address and autodiscover adjustments

data/conf/nginx/templates/nginx.conf.j2

@@ -47,6 +47,13 @@ http {
         default "";
     }
 
+    # Client address for PHP: on the internal sogo-auth listener nginx itself is the client,
+    # the real address comes from the X-Real-IP header set by /sogo-auth-verify
+    map $sogo_auth_internal $mailcow_client_ip {
+        "1"     $http_x_real_ip;
+        default $remote_addr;
+    }
+
     {% if HTTP_REDIRECT %}
     # HTTP to HTTPS redirect
     server {