title: Unity android oneSignal error on tagged push notification
body: <p>I am able to send push notifications from oneSignal web panel, but not throught my APP.
  The error is </p>
  
  <blockquote>
    <p>Segment or tag targeting requires a valid App REST API Key.</p>
  </blockquote>
  
  <p>Ok, I have my REST API key but I can`t find in the whole documentation what to do with it... Thanks</p>