This defines a new trait `Resolver`, which turns an address into a
Vec<SocketAddr>. It also provides an implementation of Resolver for
`Fn(&str)` so it's easy to define simple resolvers with a closure.
Fixes#82
Co-authored-by: Ulrik <ulrikm@spotify.com>
`Some(AgentState)` seem to be assumed pretty much everywhere. I could not
find any test or piece of code hinting at how `None` should be interpreted,
or even see how a state of `None` could even be constructed.
Co-authored-by: Ulrik <ulrikm@spotify.com>