add support to add headers to proxy

templates/vhost.conf.j2

@@ -39,6 +39,11 @@ server {
 		proxy_set_header X-Forwarded-Ssl	$https;
 		proxy_set_header X-Url-Scheme		$scheme;
 
+		# custom proxy headers
+{% for header in vhost.add_proxy_headers|d({}) if header %}
+		proxy_set_header {{ header }}		"{{ vhost.add_proxy_headers[header] }}";
+{% endfor %}
+
 		# Websockets
 		proxy_http_version 1.1;
 		proxy_set_header Upgrade $http_upgrade;