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

❌ Patch coverage is 77.77778% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.30%. Comparing base (d71538a) to head (05a578b).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...iff_drive_controller/src/diff_drive_controller.cpp	50.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1997      +/-   ##
==========================================
- Coverage   85.32%   85.30%   -0.03%     
==========================================
  Files         143      143              
  Lines       13936    13920      -16     
  Branches     1201     1198       -3     
==========================================
- Hits        11891    11874      -17     
- Misses       1638     1639       +1     
  Partials      407      407              

Flag	Coverage Δ
unittests	85.30% <77.77%> (-0.03%)	⬇️

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

Files with missing lines	Coverage Δ
...ive_controller/test/test_diff_drive_controller.cpp	93.99% <100.00%> (-0.20%)	⬇️
...iff_drive_controller/src/diff_drive_controller.cpp	82.05% <50.00%> (-0.62%)	⬇️

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[kuralme]

A note about my last commit: This is for the deprecations. I am aware of Bence's request, I will apply if a change needed to the helper source.

[christophfroehlich]

tf_frame_prefix_enable was not unused before? Instead, during the deprecation phase, we still should use this parameter before we remove it.

I'm not sure how we can gracefully transition the usage of node namespace? Currently, if tf_frame_prefix is not set, then automatically the node namespace is used.