code: public void set(final String value) {
          final User user = new User();
          user.set(value);
          users = Collections.singletonList(user);
      }
docs: Allows a user to be set by a string value. Only one user is allowed to be created via this method. The format is
  {@code user:password:groups:realm:true|false}.
  <p>
  Both username and password are required. Groups can be a comma delimited set of groups.
  </p>
  
  @param value the string user value