Fix issue where upstream only got the first query param

nginx.conf

@@ -27,7 +27,12 @@ http {
                 rewrite ^ /index.html last;
             }
 
-            proxy_pass $arg_url;
+            # Forward query string to upstream (? if url has no query, & if it already has ?)
+            set $url_sep "?";
+            if ($arg_url ~ \?) {
+                set $url_sep "&";
+            }
+            proxy_pass $arg_url$url_sep$args;
             proxy_http_version 1.1;
             proxy_set_header Host $proxy_host;
             proxy_ssl_server_name on;