AirVPN doesn't expose an endpoint to get a complete list of
servers. Theoretically, it seems possible to get this list by using
DNS. However, that's too much work. Instead, we can just generate a
single config per country. AirVPN's endpoints pick the best server so
this will work reasonably well but doesn't allow fine-grained control
over which server is being used.

In the future, one config should be generated per server.