docs: @Override
      public SearchResult getUsers(String pattern, int limit) throws RegistryException {
          if (pattern == null) {
              throw new IllegalArgumentException("pattern is null");
          }
          if (pattern.isEmpty()) {
              throw new IllegalArgumentException("pattern is an empty String");
          }
          if (limit >= 0 && user.matches(pattern)) {
              List<String> list = new ArrayList<String>();
              list.add(user);
              return new SearchResult(list, false);
          } else {
              return new SearchResult();
          }
      }