title: FirebaseMessagingService push notification creation - how to set icon?
body: <p>I want to set icon for my push notification which is created by <code>FirebaseMessagingService</code>. Problem is that these notifications are created by system internally (probably in function <code>onStartCommand()</code> which is final and I don't have access to it. I don't know from which source is icon for this notification set. Normally if you create notification you can set icon by <code>NotificationManager</code>, but this process is done internally by Firebase. Reason why I want to change icon is because my icon for app has transparent background (its vector drawable (.svg). But for some reason it is shown as square. </p>
  
  <p>Is there any way how to modify notification icon inside <code>FirebaseMessagingService</code>?</p>