title: How to resolve: 'keyWindow' was deprecated in iOS 13.0
body: <p>I'm using Core Data with Cloud Kit, and have therefore to check the iCloud user status during application startup. In case of problems I want to issue a dialog to the user, and I do it using <code>UIApplication.shared.keyWindow?.rootViewController?.present(...)</code> up to now.</p>
  
  <p>In Xcode 11 beta 4, there is now a new deprecation message, telling me:</p>
  
  <blockquote>
    <p>'keyWindow' was deprecated in iOS 13.0: Should not be used for applications that support multiple scenes as it returns a key window across all connected scenes</p>
  </blockquote>
  
  <p>How shall I present the dialog instead?</p>