Flexible item name

Now you can define product_name() method in your subclass of PayPalForm and make a custom item name (for example, to add the pricing plan into item name).

An example is available in debits_test sample application in the latest release and here:

def product_name(self, item):
    if isinstance(item, ProlongItem):
        item = item.parent
    return item.product.name + ': ' + item.purchase.plan.name