How do I display a different return-message for pass/fail/cancel

I needed this functionality, so I've created a patch to add a field: 'Failed Transaction Return URL' to the settings. You can optionally enter a path or url here where the user would be redirected if the transaction fails.

Note that there is also a separate bug fix included in this patch. There was case sensitive bug that caused the 'production' setting to be ignored. This means the test mode would always be used, irrespective of the 'Transaction mode' set (you're welcome to just extract that bug fix if you don't want to commit the whole patch).

Thanks for the patch George. I had the issue where I had changed the transaction mode from test to production and when going to the paygate site, it still showed the test page. Your patch worked to fix this issue. I also tested the fail/cancel page functionality, and it works well and is useful.

Patch commited