[FEATURE] Action to check that the generated code is up to date

[mgovers]

• the code_generation/ directory contains the code generator including its configuration.
• It is important that the generated code is up to date. i.e.:
  • no manual code changes were made to generated files; generated files should remain generated
  • the generated files are up to date with the latest code generator including its input configuration

This issue is about adding a github action check that that is indeed the case.

TODO

• [ ] Update all files in the code_generation/templates/ directory
  • [ ] Those files currently contain the string This header file is automatically generated. DO NOT modify it manually!
  • [ ] There is at least one CPP file that is clearly not a header file but does contain the string header. That is clearly wrong (as it's not a header but a CPP file)
  • [ ] Instead, the string should be: This file is automatically generated. DO NOT modify it manually!
  • [ ] Run the code_generation/code_gen.py file to update all generated files and check them in
• [ ] Create the github action
  • [ ] Install all dependencies (found in code_generation/requirements.txt)
  • [ ] Run code_generation/code_gen.py
  • [ ] Check that the git status is empty
    • [ ] should pass if it is empty
    • [ ] should fail action if it isn't empty and list the changed files
    • [ ] look up the exact command in the git documentation to do this
  • [ ] To prevent unnecessary checks, the action should only run if and only if the following checked-in files and directories are changed:
    • [ ] code_generation/
    • [ ] All files and directories that contain the string This file is automatically generated. DO NOT modify it manually!
      • [ ] In particular, those are the files that the templates code_generation/templates/ map to
      • [ ] That is: code_generation/templates/x/.../y.z maps to x/.../y.z