Fix: Use correct version of Python for poetry tests

[alexdewar]

Description

This PR changes the GitHub workflows from using the setup-poetry action to manually installing poetry via pipx instead. This fixes an issue we're seeing on the Windows runner where the runner's system version of Python is being used by poetry rather than the one we specify (i.e. 3.12).

Interestingly, we had already updated this in the workflows for the template (i.e. the ones which will end up in users' repos) but must have forgotten to do the same for this repo's workflows.

Type of change

• Documentation (non-breaking change that adds or improves the documentation)
• New feature (non-breaking change which adds functionality)
• Optimization (non-breaking, back-end change that speeds up the code)
• Bug fix (non-breaking change which fixes an issue)
• Breaking change (whatever its nature)

Key checklist

• All tests pass (eg. python -m pytest)
• Pre-commit hooks run successfully (eg. pre-commit run --all-files)

Further checks

• Code is commented, particularly in hard-to-understand areas
• Tests added or an issue has been opened to tackle that in the future. (Indicate issue here: # (issue))

[cc-a]

Do we not want poetry here?

[alexdewar]

That's a good point. As it stands it will cache the packages used by this project (i.e. cookiecutter and pytest) but not the ones used in the generated template project. I did try setting this value to poetry but it complained there was no poetry.lock in the root folder 😞

[AdrianDAlessandro]

I think using pip for cache is fine here. There are two different environments being installed, the poetry one is the one that the specification for is build dynamically by cookiecutter within this workflow

[AdrianDAlessandro]

Looks sensible, I do wonder what change in the setup-poetry action caused this to fail. It might be worth checking because it could be better than manually using pipx

[AdrianDAlessandro]

I think using pip for cache is fine here. There are two different environments being installed, the poetry one is the one that the specification for is build dynamically by cookiecutter within this workflow

[dalonsoa]

This looks fine to me. It is something we had changed in other places, so merely an oversight not changing it also here.