/**
  * Retrieves an {@link rx.Observable} which will emit an {@link OAuth2AccessToken}.
  *
  * @param userAccountEntity The user account entity to get it's access token
  * @return The OAuth access token to be emitted
  */
 public Observable<OAuth2AccessToken> loginUserAccount(UserAccountEntity userAccountEntity) {
   return mUshAccessTokenManager
       .login(userAccountEntity)
       .grantNewAccessToken()
       .doOnNext(
           oAuth2AccessToken ->
               mUshAccessTokenManager.getStorage().storeAccessToken(oAuth2AccessToken));
 }