Add debian+nix dev container

[moeffju]

This commit adds a dev container configuration file for a debian bullseye + nix container. Supporting IDEs, such as VS Code, should offer to open the cloned repository in the dev container, where users can then follow the minimal setup steps to quickly have a running dev instance without fiddling with their linux distro or nix locally.

It's a little bit more comfortable for VS Code users than the minimal docker setup.

[pajowu]

Nice, this also enables github codespaces, right?

[moeffju]

Yeah, I believe that should also enable codespaces!

It does not currently automatically run nix-shell or ./packaging/dev.sh, but that could be added.
Alternatively, dependencies can be added as dev container features, but that would be a bit messier because then there's multiple ways to manage dependencies.

[pajowu]

I think not running nix-shell or dev.sh is fine (at least for now), but could you please add some documentation on how to use this to doc/development_setup.md

[pajowu]

Also sadly this doesn't seem to work in codespaces right now due to some bug NixOS/nix#6680

[moeffju]

I tried running a codespace on my fork and it seemed to work, but I'll try again.
Pushing commits for auto-building the nix env and running packaging/dev on first container run too, and will add documentation (although there isn't a lot to say, conforming IDEs should just notify the user).

[moeffju]

Another thing that might be useful is to mount /nix into a volume so it persists between rebuilds. Currently if you rebuild the container, the nix cache is blown away as well, which is a bit annoying.

[moeffju]

Ok, I think I'm happy with this. Changes:

• Switch to nix-devcontainer, which automatically runs nix-shell shell.nix
• Use compose file to enable caching /nix in a volume
• Add onCreateCommand to initialize nix env on first container run
• Add documentation for dev container in development_setup.md

[moeffju]

$ pre-commit run --all-files
check for added large files..............................................Passed
check for merge conflicts................................................Passed
check toml...............................................................Passed
check yaml...............................................................Passed
debug statements (python)................................................Passed
fix end of files.........................................................Passed
trim trailing whitespace.................................................Passed
black....................................................................Passed
Run ruff for python files................................................Passed
Run typechecker for backend..............................................Passed
Run typechecker for worker...............................................Passed
update openapi-schema of the backend.....................................Passed
run backend tests........................................................Passed
run worker tests.........................................................Passed
eslint...................................................................Passed
openapi-typescript.......................................................Passed
tsc......................................................................Passed
format...................................................................Passed
pnpm test................................................................Passed

[pajowu]

At least in code spaces the image does not build with the following error message:

The Compose file is invalid because:
Service dev has neither an image nor a build context specified. At least one must be provided.