code: @PostAuthorize("hasRole(@configHolder.getSuperAdminRoleName()) or hasPermission(#accountName, 'READ')")
      @Transactional(readOnly = true)
      public E findByAccountName(String accountName) {
          return dao.findByAccountName(accountName);
      }
docs: Returns the user for the given (unique) account name.
  If no user was found, null will be returned.
  
  @param accountName A unique account name.
  @return The unique user for the account name or null.