Feature: A Mostro can define which fiat currencies can be exchanged on it.

[Catrya]

A Mostro operator should be able to decide which fiat currencies can be exchanged on their Mostro, so as not to have to deal with disputes or any issues associated with orders using a fiat currency that they has no experience with. By default, any currency should be allowed, but if the admin decides to set a certain number of currencies, they should be able to do so.

Users should be able to know which currencies a Mostro allows, so perhaps that information could be added to the event of Mostro Instance Status