docs: public static WebClient setHeader(WebClient webClient) {
  		Properties properties = getInstance().getHeader();
  		Enumeration<Object> keys = properties.keys();
  		while (keys.hasMoreElements()) {
  			String key = (String) keys.nextElement();
  			webClient = webClient.header(key, properties.getProperty((String) key));
  		}
  		return webClient;
  	}