ios: fix cancellation when setting up screen lock

When you cancel the screen lock setup during auth, the app would get
stuck on an empty 'authenticate' screen. We needed to call
MobileserverCancelauth instead so the app handles cancellation properly.

Author: benma

frontends/ios/BitBoxApp/BitBoxApp/BitBoxAppApp.swift

@@ -9,26 +9,6 @@ import SwiftUI
 import Mobileserver
 import LocalAuthentication
 
-func authenticateUser(completion: @escaping (Bool) -> Void) {
-    let context = LAContext()
-    var error: NSError?
-
-    if context.canEvaluatePolicy(.deviceOwnerAuthentication, error: &error) {
-        // TODO: localize the reason string.
-        let reason = "Authentication required"
-        context.evaluatePolicy(.deviceOwnerAuthentication, localizedReason: reason) { success, authenticationError in
-            DispatchQueue.main.async {
-                completion(success)
-            }
-        }
-    } else {
-        // Biometric authentication not available
-        DispatchQueue.main.async {
-            completion(false)
-        }
-    }
-}
-
 protocol MessageHandlersProtocol {
     func callResponseHandler(queryID: Int, response: String)
     func pushNotificationHandler(msg: String)
@@ -53,9 +33,31 @@ class GoEnvironment: NSObject, MobileserverGoEnvironmentInterfaceProtocol, UIDoc
     }
 
     func auth() {
-        authenticateUser { success in
-            // TODO: enabling auth but entering wrong passcode does not remove auth screen
-            MobileserverAuthResult(success)
+        let context = LAContext()
+        var error: NSError?
+
+        if context.canEvaluatePolicy(.deviceOwnerAuthentication, error: &error) {
+            // TODO: localize the reason string.
+            let reason = "Authentication required"
+            context.evaluatePolicy(.deviceOwnerAuthentication, localizedReason: reason) { success, authenticationError in
+                DispatchQueue.main.async {
+                    if success {
+                        MobileserverAuthResult(true);
+                    } else {
+                        if let laError = authenticationError as? LAError,
+                           laError.code == .userCancel {
+                            MobileserverCancelAuth();
+                        } else {
+                            MobileserverAuthResult(false);
+                        }
+                    }
+                }
+            }
+        } else {
+            // Biometric authentication not available
+            DispatchQueue.main.async {
+                MobileserverAuthResult(false);
+            }
         }
     }
 
@@ -67,7 +69,7 @@ class GoEnvironment: NSObject, MobileserverGoEnvironmentInterfaceProtocol, UIDoc
         if !bluetoothManager.isConnected() {
             return nil
         }
-       
+
         let productInfo = bluetoothManager.parseProduct();
         guard let productInfo = productInfo else {
             // Not ready or explicitly not connected (waiting for the device to enter