code: String resetSubject(long sessionId) {
      if (prefix == null) {
        return String.format("reset-%d", sessionId);
      } else {
        return String.format("%s-reset-%d", prefix, sessionId);
      }
    }
docs: Returns the reset subject for the given session.
  
  @param sessionId the session for which to return the reset subject
  @return the reset subject for the given session