Store user location when redirected to register

When checking out, if a user is not registered, they will be redirected
to the registration path. This path does not need to be authenticated
and therefore will not have the user's last location stored. We need to
store the user's location if redirected.

Author: cpfergus1

lib/decorators/frontend/controllers/spree/checkout_controller_decorator.rb

@@ -45,6 +45,7 @@ def check_authorization
     def check_registration
       return unless registration_required?
 
+      store_spree_user_location!
       redirect_to spree.checkout_registration_path
     end