[CM] Add message field to the switch_controller service

[saikishor]

As we discussed in the previous WG meeting, I've added the message field to the SwitchControllers service response. This message is also integrated into the CLI

[codecov]

Codecov Report

Attention: Patch coverage is 67.69231% with 42 lines in your changes missing coverage. Please review.

Project coverage is 89.40%. Comparing base (3aa38b0) to head (4d16c0b).

Files with missing lines	Patch %	Lines
controller_manager/src/controller_manager.cpp	67.69%	36 Missing and 6 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2088      +/-   ##
==========================================
- Coverage   89.54%   89.40%   -0.14%     
==========================================
  Files         139      139              
  Lines       15125    15237     +112     
  Branches     1283     1292       +9     
==========================================
+ Hits        13543    13622      +79     
- Misses       1096     1125      +29     
- Partials      486      490       +4     

Flag	Coverage Δ
unittests	89.40% <67.69%> (-0.14%)	⬇️

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

Files with missing lines	Coverage Δ
.../include/controller_manager/controller_manager.hpp	96.87% <ø> (ø)
controller_manager/src/controller_manager.cpp	75.74% <67.69%> (-0.53%)	⬇️

... and 2 files with indirect coverage changes

[christophfroehlich]

works great, some minor comments

[christophfroehlich]

Nice work!