UserManager.java

//UserManager
public Observable<User> startSessionForUser(String username) {
    return githubApiService.getUser(username)
            .map(User.UserResponseToUser())
            .doOnNext(new Action1<User>() {
                @Override
                public void call(User user) {
                    userDataStore.createUser(user);
                    startUserSession();
                }
            })
            .subscribeOn(Schedulers.io())
            .observeOn(AndroidSchedulers.mainThread());
}

private boolean startUserSession() {
    User user = userDataStore.getUser();
    if (user != null) {
        Timber.i("Session started, user: %s", user);
        userComponent = userComponentBuilder.sessionModule(new UserModule(user)).build();
        return true;
    }

    return false;
}