code: public SoapServerFaultResponseActionBuilder attachment(String contentId, String contentType, Resource contentResource, Charset charset) {
          SoapAttachment attachment = new SoapAttachment();
          attachment.setContentId(contentId);
          attachment.setContentType(contentType);
  
          try {
              attachment.setContent(FileUtils.readToString(contentResource, charset));
          } catch (IOException e) {
              throw new CitrusRuntimeException("Failed to read attachment resource", e);
          }
  
          getAction().getAttachments().add(attachment);
  
          return this;
      }
docs: Sets the attachment with content resource.
  @param contentId
  @param contentType
  @param contentResource
  @param charset
  @return