feat: Dockerfile generator

[develop7]

Introduces a Dockerfile generator in an attempt to finally eliminate the copy&paste.

The generator is essentially a program that feeds template/Dockerfile.jinja template (in the (in)famous Jinja syntax; powered by our own Ginger) with the data from YAML files scattered across the repository and prints a Dockerfile. The choice of Jinja for templates and YAML for data is a middle ground between correctness and accessibility. Generated Dockerfiles are supposed to be checked in to version control regardless, so it doesn't change much the workflow as a whole — it just makes updating images along almost trivial, eliminating the most tedious part of the maintainer's job.

I also took the liberty to enhance the Dockerfile template slightly, in particular:

• converted RUN stanzas to heredoc syntax dropping these nasty \; trails on every line
• upgraded ENV stanzas so the build won't fail
• wrapped raw strings with quotes where applicable, just in case

Things to fix:

• make generator easier to run by wrapping it to generate.sh or something. @jhrcek @chreekat I'm open for suggestions.

[jhrcek]

Having some automation around this makes sense to me as long as we're keeping the generated dockerfiles in git. I don't see any immediate issues with this, so 👍 from me

[develop7]

Having some automation around this makes sense to me as long as we're keeping the generated dockerfiles in git. I don't see any immediate issues with this, so 👍 from me

Yes, I could not agree more and that was the intent from the day 0. Let's merge and see how it works.

[chreekat]

Nice work! As a followup, maybe we could have a GitHub workflow that confirms that the generated Dockerfiles are in sync with the generator script. :)