CI(black): Post black code suggestions as PR review comments

[echoix]

Since #3527 is merged, I rebased my implementation of posting code suggestions for Black formatting.
I have implemented a pattern to handle multiple tools in the workflow_run triggered workflow (the one called when a workflow is completed, and that runs with write permissions, and from the context of the default branch->main).

I wrote the workflow with a whitelisting approach in mind, to only allow continuing on the expected file names, in case the workflow is triggered on a file that wasn’t supposed to.
That’s why it’s not a simple loop, that would execute shell scripts on untrusted inputs/interpolation.

[echoix]

Next step: upgrading the black version for the repo, whilst having this tool to help out PRs with the transition.

[echoix]

I'd like to have this reviewed today, so I can chain up the rest during the long weekend. You can see this in action in the grass-addons repo. It worked as intended end of day yesterday.

[petrasovaa]

I am approving this, but note this is not my area of expertise...

[echoix]

Sorry, I went more with the Python part, but in fact, there's no Python here... it's for Python...

Do you think it is useful though, on a user perspective?

[petrasovaa]

Sorry, I went more with the Python part, but in fact, there's no Python here... it's for Python...

Do you think it is useful though, on a user perspective?

Sorry, I went more with the Python part, but in fact, there's no Python here... it's for Python...

Do you think it is useful though, on a user perspective?

I would hope so, if I understand this correctly, this is most helpful for newcomers and perhaps maintainers.