code: private StitchUserT doLogin(final StitchCredential credential, final boolean asLinkRequest) {
      final Response response = doLoginRequest(credential, asLinkRequest);
  
      final StitchUserT previousUser = activeUser;
      final StitchUserT user = processLoginResponse(credential, response, asLinkRequest);
  
      if (asLinkRequest) {
        onUserLinked(user);
      } else {
        onUserLoggedIn(user);
        onActiveUserChanged(activeUser, previousUser);
      }
  
      return user;
    }
docs: callers of doLogin should be serialized before calling in.