eCommerce: charge payment fee

This module lets you configure a fee on each payment provider (like a credit card surcharge). In the payment provider form, a new 'Charge payment fee' tab appears where you can enable the fee, choose a service product to represent it, and set either a fixed amount or a percentage of the order total. You can also set the currency for fixed fees.

On the website shop, when a customer selects a payment method that has a fee, the fee is automatically added as a separate line to the order. The fee line is hidden from the normal cart lines but shown in the order total summary as 'Payment Fee'. The fee amount is recalculated whenever the order changes or the payment method is switched.

The fee is computed based on the order subtotal (tax excluded) or total (tax included), depending on the website setting for showing subtotals. If the fee currency differs from the order currency, the fixed fee is converted automatically.

This module affects payment providers, sale orders, and sale order lines. It also modifies the website payment form to display the fee next to the payment method and to refresh the order total when a method is selected.