title: Does apps on Google Play allows a log in mechanism to unlock features that same as in-app purchase?
body: <p>Our app is not currently on Google Play, but it has been released to other channels for a period of time. The app can be downloaded and used for free, but some functions need to be unlocked with purchase. The current way of unlocking is to purchase an activation code on the website and bind an account, and then Login in the app.</p>
  <p>Google Play has to use Google's billing system for purchasing and unlocking the app's functionality for sure, I was thinking what if the version of the app that released on Google Play has a mechanism to also let our users to login with their existing account to continue use our app with paid functions, will this be rejected by Google?</p>