CreateResolver creates a HostnameResolver.

Full is the FDQN hostname.

Short is the short hostname.

ShortAndFull both were changed.

ChangeNotification is the struct being sent through the notification channel.

ChangeNotifier allows observer to register a channel to be notified of when the hostname is updated.

Resolver provides full and short name resolving functionalities.

ResolverChangeNotifier is a sum of both Resolver and ChangeNotifier interfaces.

ChangeType represents the type of hostname change.