docs: public void validateParameters(CmsObject cms) {
  
          CmsMessages messages = Messages.get().getBundle(getLocale());
          StringBuffer validationErrors = new StringBuffer();
          if (CmsStringUtil.isEmpty(getParamFolder1())) {
              validationErrors.append(messages.key(Messages.GUI_MERGE_PAGES_VALIDATE_FIRST_FOLDER_0)).append("<br>");
          } else {
              try {
                  cms.readResource(getParamFolder1());
              } catch (CmsException e) {
                  validationErrors.append(
                      messages.key(Messages.GUI_MERGE_PAGES_VALIDATE_FIRST_FOLDER_1, getParamFolder1())).append("<br>");
              }
          }
          if (CmsStringUtil.isEmpty(getParamFolder2())) {
              validationErrors.append(messages.key(Messages.GUI_MERGE_PAGES_VALIDATE_SECOND_FOLDER_0)).append("<br>");
          } else {
              try {
                  cms.readResource(getParamFolder2());
              } catch (CmsException e) {
                  validationErrors.append(
                      messages.key(Messages.GUI_MERGE_PAGES_VALIDATE_SECOND_FOLDER_1, getParamFolder2())).append("<br>");
              }
          }
          if (getParamFolder1().equals(getParamFolder2())) {
              validationErrors.append(messages.key(Messages.GUI_MERGE_PAGES_VALIDATE_SAME_FOLDER_0)).append("<br>");
          }
  
          setErrorMessage(validationErrors.toString());
      }