configure a default payment currency for fx payments


User should be able to select a currency as default currency for payments in other currencies that user doesnt hold enough balance

I am holding different currencies, at some point i want to be able to tell revolut to bill from USD instead of EUR even if I hold more EUR.

This feature would also make it more clear for users to see from what account users eventually pay as it would visually display a label saying “default” or “spend from here” on the account thats holding the most money and automatically switch from one account to another depending on how one tops up or spends.