Our client has a need to allow customers to send a very simple 1 time payment amount. An example would be the customer wasn't charged enough shipping, or the original invoice paid was the incorrect amount and they owe a small balance, etc.
they would like it to be as simple as possible, ie a single page where the customer fills in the amount they want to pay, along with the credit card details and that's it, no shipping, no tax, etc...
We already have a full cart/checkout system working with foxycart, and I'm wondering if you have any suggestions on how best to approach this request?
a few ideas i had
1) create a new store for this feature so I can turn off shipping, and tax, etc but I would still need ask the user to go through 2 steps right? one for filling in the product data and another for the checkout page?
2) somehow using the foxy api to submit everything from a single page? is this possible?
3) perhaps changing the workflow to where my client fills out the cart amount and then send their customer directly to the checkout page using the URL of that unique cart, is there a time limit on passing urls like that? would it expire or not work as intended?
any other suggestions?