BelongsTo (allows a Grav instance to self-identify as belonging to a group, and controls which other instances it meshes with - handshakes with other groups get rejected)
Capabilities (allows self-identification of an instance's capabilities, allowing others to use Tunnel)
Tunnel (allows an instance to send a message to a single meshed instance that has broadcasted a particular capability, bypassing the core bus and load balancing among the instances that advertise the given capability)
This adds 3 things:
See
transport/websocket/tester.gofor use,