Create "Access denied" page
Closed, ResolvedPublic2 Story Points

Description

Currently when the access token for a PayPal donation doesn't match on the confirmation page, you just get the text TODO: access not permitted. There should be a general 'access denied' route with an error message and a 403 status code for this. app/RouteHandlers/ShowDonationConfirmationHandler.php and other places where the user expects an HTML response, should forward (not redirect) to this route.