code: public Metrics ping() {
      bindings.add((binder, routes, conf) -> {
        routes.use("GET", this.pattern + "/ping", new PingHandler());
      });
      return this;
    }
docs: Append a simple ping handler that results in a <code>200</code> responses with a
  <code>pong</code> body. See {@link PingHandler}
  
  @return This metrics module.