I could not extract the open_drone_id helpers to a separate lib because
it would require the mavlink headers while the mavlink library would
also depend on it, so it ended up being a circular dependency.
Instead, I'm now just using the headers from within the mavlink module
as well as from the uavcan driver.
This will send the System message if it is already being sent by a ground
station. Otherwise, it will assemble the message itself using the
takeoff/home location.
Julian Oes