Referencing the type of payment after external gateway redirect

[jedateach]

After we are redirected from an external gateway back to our website, how do we reference the type of payment, gateway used, and controller type?

Essentially we need to store something in the url that we provide to the external gateway, which can be later referenced to restore the payment type, and continue processing.

What to store:

• Payment identifier - new concept introduced recently for the registry/factory - current preferred option
• A class name

Where to store:

• Store payment type (identifier?) on the model - current preferred option
• Store in a url parameter
• Enforce a controller and rule for every payment type
• Session?

This brings up more questions however. We're starting to rely more on this unified 'payment identifier' concept, which hasn't been thought through really well.