code: @Get("/header")
      public HttpResponse header(@Header String xArmeriaText,            /* no conversion */
                                 @Header List<Integer> xArmeriaSequence, /* converted into integer */
                                 Cookies cookies                         /* converted into Cookies object */)
              throws JsonProcessingException {
          return HttpResponse.of(HttpStatus.OK, MediaType.JSON_UTF_8, mapper.writeValueAsBytes(
                  Arrays.asList(xArmeriaText,
                                xArmeriaSequence,
                                cookies.stream().map(Cookie::name).collect(Collectors.toList()))));
      }
docs: Returns the received {@code x-armeria-text}, {@code x-armeria-sequence}, {@code Cookie} headers
  to the sender as a JSON list.