code: public static boolean isCorsPreflightRequest(com.linecorp.armeria.common.HttpRequest request) {
          requireNonNull(request, "request");
          return request.method() == HttpMethod.OPTIONS &&
                 request.headers().contains(HttpHeaderNames.ORIGIN) &&
                 request.headers().contains(HttpHeaderNames.ACCESS_CONTROL_REQUEST_METHOD);
      }
docs: Returns {@code true} if the specified {@code request} is a CORS preflight request.