Gets one commission. Send `expand=transaction` to get the payment or refund it is for. Secret and trusted tokens may call it; a limited token may not (`403`).

Convert an amount GET

Converts an amount from one currency to another at today's rate, with the same rules your shop uses for prices (your markup and rounding in Settings, Pricing). Pass a `cart_id` or `invoice_id` to use the rate saved on that cart or invoice instead of today's. Secret and trusted tokens may call this. No permission is needed. Limited tokens are refused (`403`): use `GET /fx/product` in the browser.