docs: protected Response responseForFileVariable(FileValue fileValue) {
      String type = fileValue.getMimeType() != null ? fileValue.getMimeType() : MediaType.APPLICATION_OCTET_STREAM;
      if (fileValue.getEncoding() != null) {
        type += "; charset=" + fileValue.getEncoding();
      }
      Object value = fileValue.getValue() == null ? "" : fileValue.getValue();
      return Response.ok(value, type).header("Content-Disposition", "attachment; filename=" + fileValue.getFilename()).build();
    }