docs: @Nonnull
    public ELoginResult loginUser (@Nullable final String sLoginName,
                                   @Nullable final String sPlainTextPassword,
                                   @Nullable final Iterable <String> aRequiredRoleIDs)
    {
      // Try to resolve the user
      final IUser aUser = PhotonSecurityManager.getUserMgr ().getUserOfLoginName (sLoginName);
      if (aUser == null)
      {
        AuditHelper.onAuditExecuteFailure ("login", sLoginName, "no-such-loginname");
        return ELoginResult.USER_NOT_EXISTING;
      }
      return loginUser (aUser, sPlainTextPassword, aRequiredRoleIDs);
    }