NearbySite
data class NearbySite(val id: String, val name: String, val address: String, val requiresCode: Boolean)
A site heard on the local network (see Beacons): its identifier, its name (the name of its host, or the one it was given), its address (ws://host:port) and whether it requires a code of the sites linking to it (requiresCode: it waits to be paired)