Altering/Adding Submit Behavior in Checkout
Suppose I have Checkout Page 1 with Checkout Pane 1 and Checkout Pane 2.
Checkout Pane 2 is a customer billing profile pane, provided by the built-in billing profile. Checkout Pane 1 is a creation of my own.
There is information I'd like to add to the billing profile from Pane 1. Passing data into the order with $order->data[pane_1] is easy in the submit callback for Pane 1 ... but where do I look to add some submit behavior to the billing profile pane?