AutoNATConfig defines the AutoNAT behavior for the libp2p host.

Config describes a set of settings for a libp2p node This is *not* a stable interface.

AddrsFactory is a function that takes a set of multiaddrs we're listening on and returns the set of multiaddrs we should advertise to the network.

NATManagerC is a NATManager constructor.

Option is a libp2p config option that can be given to the libp2p constructor (`libp2p.New`).