Update callback to update invoices using reference number instead of ID

[thisisayush]

Fixes #138

Using the id_order stored, the order with the same reference number is fetched, and all the underlying orders are then updated for paid status.

[thisisayush]

E.g. Orders with same reference are updated when payment is received

[DarrenWestwood]

This is working well at marking all the orders as paid/underpaid respectively.

Paid: Is there a better way of handling the split payments saved to the order? Either by only linking the relative payment to the order, as with underpayments, or ensuring each payment has the txid?

Underpayment:

[thisisayush]

Split payments are handled automatically by Prestashop, actual payment is recoded against the reference of order at once. Will look more into it to see what can be done.

This is related to the following epic on Prestashop, https://github.com/PrestaShop/PrestaShop/issues/15491

[thisisayush]

PS Validator Passed ✅