Set pg_service_name using PerlSetEnv instead of PerlSetVar as ->dir_config() is not always available in Plack requests without being ugly.
Set TermURL to pci-blackbox and invoke submit_paresponse().
Use ->parameters() instead of ->body_parameters() as we need to pass "authoriserequestid" as a query param while the rest will be submitted in the POST data. Also read pg_service_name from %ENV instead of ->dir_config().