How to transfer data after payment?

Question

MODX

An order is placed on the site (MODX REVO) through Shopkeeper 3, and when choosing online payment, the user is redirected to Yandex.Checkout.
After successful payment for the order, you need to save the buyer's data specified during the order in JSON format for further transfer to the user's account.
The order form is executed through FormIt, then the data is transferred to the cashier.
I didn’t have to work with online payments, in which direction should I look? I found in the Yandex API that the data is transmitted in JSON format, but the user is registered in Shopkeeper without payment, but immediately after the order.

Answer 1

without being tied to specific cms and payment systems.
All the necessary information is already stored in advance.
At the moment paymentAviso is received, it is only checked
that the hook call is not faked (came from the right ip, signed correctly,
we are waiting for such a payment, that this is not a repeated notification, the
amount and currency of the payment is required.
Now, at this moment, 54-FZ is being added about fiscalization of the payment.
) after which the document is marked as paid.