ROS Callback Group §

First saw this when developing for MIT-PITT-RW.

https://docs.ros.org/en/humble/How-To-Guides/Using-callback-groups.html

Seems like it was because they were running into DDS buffering issues?

When running a node in a Multi-Threaded Executor, ROS 2 offers two different types of callback groups for controlling execution of callbacks:

1. Mutually Exclusive Callback Group
2. Reentrant Callback Group