private void generateConfig(PrintWriter xml, ConfigInstance config) throws Exception {
                Field nameField = config.getClass().getField("CONFIG_DEF_NAME");
                String name = (String) nameField.get(config);
                Field namespaceField = config.getClass().getField("CONFIG_DEF_NAMESPACE");
                String namespace = (String) namespaceField.get(config);

                xml.println("<config name=\"" + namespace + "." + name + "\">");
                generateConfigNode(xml, config);
                xml.println("</config>");
            }
@param config add this config to the application
@return builder
application/src/main/java/com/yahoo/application/Application.java