Use ISO codes instead of country names for VAT MOSS

When trying to explain a transaction as VAT MOSS using the API we are asked for “place_of_supply” which is the country the sale was in.

At the moment this expects a specific string of the country name.

Would it not be better to accept two or three letter ISO codes? Pretty much every piece of software represents nations using these codes so it’s frustrating to have to implement a separate conversion to the country names that Free Agent requires.

It would also avoid any issues with variations in country names, since ISO codes are a fixed standard.