use woocommerce-friendly authentication URL

Signed-off-by: David Seaward <david.seaward@puri.sm>

cart/views.py

@@ -52,20 +52,21 @@ class CartRegistrationView(RegistrationView):
     def get_success_url(self, user):
 
         if self.reward in ["0", "999"]:
-            # skip billing requirements
+            # skip billing page for magic cart numbers
+            # (but still force authentication for login purposes)
 
-            url = '{}/{}?{}'.format(
+            url = '{}/{}/{}&reauth=1'.format(
                 settings.WOO_URL,
-                'wp-login.php?redirect=',
+                'wp-login.php?redirect_to=',
                 settings.WOO_CART_THANKS_PATH,
             )
 
         else:
             # go to WooCommerce cart URL
 
-            url = '{}/{}/{}?{}'.format(
+            url = '{}/{}/{}?{}&reauth=1'.format(
                 settings.WOO_URL,
-                'wp-login.php?redirect=',
+                'wp-login.php?redirect_to=',
                 settings.WOO_CART_BILLING_PATH,
                 self.reward
             )