title: What happens if I disable IS_GCM_ENABLED key to false in Google-Service-info.plist
body: <p>I have application which has Firebase Push Notifications. </p>
  
  <p>I changed <code>IS_GCM_ENABLED</code> key to false in Google-Service-info.plist on Xcode. </p>
  
  <p>But push notifications works perfectly and why push notification works even I changed key to false?</p>
  
  <p>Could you explain for what we use these keys in Google-Service-info.plist
  <code>
  IS_GCM_ENABLED,
  IS_SIGNIN_ENABLED,
  IS_APPINVITE_ENABLED,
  IS_ANALYTICS_ENABLED,
  IS_ADS_ENABLED,
  </code></p>
  
  <p>As I know GCM changed to FCM and Why in Google-Service-info.plist we use <code>IS_GCM_ENABLED</code> not <code>IS_FCM_ENABLED</code>? </p>
  
  <p>Why <code>IS_FCM_ENABLED</code> key doesn't exists in Google-Service-info.plist?</p>