Use case: Enable a robot to be extended with different tools

[destogl]

A robot as ros2_control structure should be extensible with additional tools, e.g. force-torque sensor, milling machine, etc. This extension should be transparent for controllers by adding new data in the DynamicJointState message. It is preferable to do this without any coding and just loading additional sensor component, i.e. hardware_interface (i the case that sensors is ros2_control enabled).