TF prefix helper for diff drive controller

[kuralme]

Used new tf frame prefix helper in differential drive controller to test out & showcase the helper. This is the first part of the changes, the other controllers will come next:

• mecanum_drive_controller
• omni_wheel_drive_controller

Related issue

[saikishor]

I'm not sure if it makes sense to have it in the control_toolbox package. What about controllers_interfaces/helpers.hpp existing file?

What do you think @christophfroehlich ?

[christophfroehlich]

I'm not sure if it makes sense to have it in the control_toolbox package. What about controllers_interfaces/helpers.hpp existing file?

OK, maybe you are right and we should put it here.

[kuralme]

I'm not sure if it makes sense to have it in the control_toolbox package. What about controllers_interfaces/helpers.hpp existing file?

OK, maybe you are right and we should put it here.

I will start working on it

[christophfroehlich]

There is a behavior-breaking change now, right?
Can we do that gracefully? e.g.,

• Deprecate the tf_frame_prefix_enable parameter in the yaml, and log a warning message if it is set to a value different than default. And we should maintain the behavior and still use the value.
• Please update the description of the tf_frame_prefix parameter
  https://github.com/ros-controls/ros2_controllers/blob/master/diff_drive_controller/src/diff_drive_controller_parameter.yaml#L49-L53
• Please add release and migration notes.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.28%. Comparing base (c38468c) to head (53851e8).
⚠️ Report is 4 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1997      +/-   ##
==========================================
- Coverage   85.32%   85.28%   -0.04%     
==========================================
  Files         143      143              
  Lines       13934    13857      -77     
  Branches     1201     1193       -8     
==========================================
- Hits        11889    11818      -71     
+ Misses       1638     1634       -4     
+ Partials      407      405       -2     

Flag	Coverage Δ
unittests	85.28% <100.00%> (-0.04%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...iff_drive_controller/src/diff_drive_controller.cpp	82.55% <100.00%> (-0.13%)	⬇️
...ive_controller/test/test_diff_drive_controller.cpp	93.99% <100.00%> (-0.20%)	⬇️

... and 1 file with indirect coverage changes

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