Add documentation and cleanups for PlanningRequestAdapter and PlanningRequestAdapterChain classes

[sjahr]

Description

• Documentation & Cleanups for PlanningRequestAdapter & PlanningRequestAdapterChain classes

Checklist

• Required by CI: Code is auto formatted using clang-format
• Extend the tutorials / documentation reference
• Document API changes relevant to the user in the MIGRATION.md notes
• Create tests, which fail without this PR reference
• Include a screenshot if changing a GUI
• While waiting for someone to review your request, please help review another open pull request to support the maintainers

[codecov]

Codecov Report

Patch coverage: 14.29% and project coverage change: +0.01 🎉

Comparison is base (f807733) 50.47% compared to head (58e449f) 50.48%.

❗ Current head 58e449f differs from pull request most recent head 14fa91e. Consider uploading reports for the commit 14fa91e to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2142      +/-   ##
==========================================
+ Coverage   50.47%   50.48%   +0.01%     
==========================================
  Files         387      387              
  Lines       31790    31785       -5     
==========================================
  Hits        16043    16043              
+ Misses      15747    15742       -5     

Impacted Files	Coverage Δ
...core/planning_interface/src/planning_interface.cpp	60.00% <0.00%> (ø)
...or/src/current_state_monitor_middleware_handle.cpp	88.89% <0.00%> (ø)
...include/moveit_setup_app_plugins/launch_bundle.hpp	0.00% <0.00%> (ø)
...ework/include/moveit_setup_framework/templates.hpp	25.00% <ø> (ø)
...sistant/moveit_setup_framework/src/srdf_config.cpp	68.58% <0.00%> (ø)
.../moveit_setup_srdf_plugins/src/planning_groups.cpp	8.20% <0.00%> (ø)
...assistant/moveit_setup_framework/src/templates.cpp	67.86% <100.00%> (ø)

... and 1 file with indirect coverage changes

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[henningkayser]

I approve these changes in general. But why did you mix in the fixes for MSA and PSM, they don't seem related at all?

[sjahr]

I approve these changes in general. But why did you mix in the fixes for MSA and PSM, they don't seem related at all?

I thought it makes sense to apply the return std::string(); mini fix everywhere (probably should have done this in a separate PR, sorry) and the variables_ renaming was due to the CI error.

[sjahr]

@henningkayser I cleaned it up