This can be used to command multiple devices on the UAVCAN bus to
update their LEDs. This will come in handy for status outputs etc.
This utilizes equipment.indication.LightsCommand message.
This message is not so important and therefore we limit publishing
it to avoid bus overflow. The priority of the message is also low.
To do so, we make use of UAVCAN message MagneticFieldStrength2, which
has a field describing the sensor_id of the node which measurements were
sent, and if a node sends this message we register multiple
AP_Compass_UAVCAN backends for this node. The routing of the messages
between those backends is also implemented here.