Fix logging in on iOS 13

Tusker/Screens/Onboarding/OnboardingViewController.swift

@@ -69,6 +69,7 @@ class OnboardingViewController: UIViewController {
                     }
                 }
             }
+            self.authenticationSession!.presentationContextProvider = self
             self.authenticationSession!.start()
         }
     }
@@ -81,3 +82,9 @@ class OnboardingViewController: UIViewController {
     }
 
 }
+
+extension OnboardingViewController: ASWebAuthenticationPresentationContextProviding {
+    func presentationAnchor(for session: ASWebAuthenticationSession) -> ASPresentationAnchor {
+        return UIApplication.shared.delegate!.window!!
+    }
+}