Integer initialPosition coordinates in crazyflies.yaml

[jpreiss]

This PR should be "squash and merge"d into one commit.

See motivating discussion in #380.

I wanted to add a CI test that starts the server and looks for the "Parsed crazyflies.yaml successfully" message on stdout before the server fails due to no radio or CFs existing. However, the server tries to open the radio on USB before it finishes parsing.

It would be nice if the config-parsing and hardware connection were two cleanly separated phases in the server, but the problem is that we initialize the CrazyflieBroadcaster member in the initializer list of CrazyflieGroup:

crazyswarm/ros_ws/src/crazyswarm/src/crazyswarm_server.cpp

Line 810 in 957d663

, m_cfbc("radio://" + std::to_string(radio) + "/" + std::to_string(channel) + "/2M/FFE7E7E7E7")

To fix this enough for single-group testing, we would need to move the broadcaster initialization to the end of the CrazyflieGroup constructor, either by giving CrazyflieBroadcaster a separate init method or using a pointer. However, to fix it enough for multi-group testing, we would need to give CrazyflieGroup itself a separate init method, so we can finish parsing for all of the channels before attempting to connect to any of them.

I think this would be a design improvement, but maybe should be deferred until after the link-cpp version.

[whoenig]

Switching to link-cpp won't change much on the server side (see the existing branch), so we could do your suggested changes already. I don't see it as a very high priority, though (this parsing code will change for the ROS2 port, unfortunately).