Every IRC server we support (other than Bahamut which is probably
on the chopping bock) uses UIDs so this setting does nothing.

Instead, allow configuring a server-side alias for each service
and use that when servicealias is enabled.

Having these throw is terrible for ergonomics and there are loads
of places where the exception was either silently ignored or not
handled at all. Having a function which returns an optional and
another that returns a default works a lot better imo.