Docker: Forward real hostname instead of "localhost"

docker/etc/nginx/nginx.conf

@@ -42,6 +42,7 @@ http {
             fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
             fastcgi_index index.php;
             include fastcgi_params;
+            fastcgi_param SERVER_NAME $host;
         }
 
         location ~ /data {