docs: protected void init(
          String userAdmin,
          String userGuest,
          String userExport,
          String userDeletedResource,
          String groupAdministrators,
          String groupUsers,
          String groupGuests) {
  
          // check if all required user and group names are not null or empty
          if (CmsStringUtil.isEmptyOrWhitespaceOnly(userAdmin)
              || CmsStringUtil.isEmptyOrWhitespaceOnly(userGuest)
              || CmsStringUtil.isEmptyOrWhitespaceOnly(userExport)
              || CmsStringUtil.isEmptyOrWhitespaceOnly(groupAdministrators)
              || CmsStringUtil.isEmptyOrWhitespaceOnly(groupUsers)
              || CmsStringUtil.isEmptyOrWhitespaceOnly(groupGuests)) {
              throw new CmsRuntimeException(Messages.get().container(Messages.ERR_USER_GROUP_NAMES_EMPTY_0));
          }
          // set members
          m_userAdmin = userAdmin.trim();
          m_userGuest = userGuest.trim();
          m_userExport = userExport.trim();
          if (CmsStringUtil.isEmptyOrWhitespaceOnly(userDeletedResource)) {
              m_userDeletedResource = userAdmin;
          } else {
              m_userDeletedResource = userDeletedResource.trim();
          }
          m_groupAdministrators = groupAdministrators.trim();
          m_groupUsers = groupUsers.trim();
          m_groupGuests = groupGuests.trim();
      }