feat: add basic support for nix flakes

[isubasinghe]

This adds a reproducible build environment for Argo Workflows. Argo Workflows can now be run in a few simple steps documented in the README.md.

Why are there some go files changed here?
This was the outcome of running gofmt on the sources, sources can be reformatted by running "nix fmt".
Currently this only supports formatting golang and nix files but can be extended to anything supported via clang-format, prettier and more. See this for more info: https://numtide.github.io/treefmt/formatters/

The files.go stub was added, this is a bit more deterministic than copying at build time. This will also make caching easier.

[JPZ13]

I'm running into an error with devenv up

(devenv) JPs-MacBook-Pro:argo-workflows jpzivalich$ devenv up
mkdir: /.devenv: Read-only file system
/nix/store/3hbmx5ka5k6m9hijylj0skri9wfp6rag-devenv-up: line 22: /.devenv/state/devenv.pid: No such file or directory
11:23:55 system                | ui.1 started (pid=2625)
11:23:55 system                | argo-server.1 started (pid=2626)
11:23:55 system                | workflow-controller.1 started (pid=2627)
11:23:55 workflow-controller.1 | time="2023-05-02T11:23:55+02:00" level=info msg="index config" indexWorkflowSemaphoreKeys=true
11:23:55 workflow-controller.1 | time="2023-05-02T11:23:55+02:00" level=info msg="cron config" cronSyncPeriod=10s
11:23:55 workflow-controller.1 | time="2023-05-02T11:23:55+02:00" level=info msg="Memoization caches will be garbage-collected if they have not been hit after" gcAfterNotHitDuration=30s
11:23:55 workflow-controller.1 | time="2023-05-02T11:23:55.369Z" level=info msg="not enabling pprof debug endpoints"
11:23:55 workflow-controller.1 | time="2023-05-02T11:23:55.441Z" level=info msg="Get configmaps 404"
11:23:55 workflow-controller.1 | time="2023-05-02T11:23:55.442Z" level=fatal msg="Failed to register watch for controller config map: configmaps \"workflow-controller-configmap\" not found"
11:23:55 system                | workflow-controller.1 stopped (rc=1)
11:23:55 system                | sending SIGTERM to argo-server.1 (pid 2626)
11:23:55 system                | sending SIGTERM to ui.1 (pid 2625)
11:23:55 system                | argo-server.1 stopped (rc=-15)
11:23:55 system                | ui.1 stopped (rc=-15)
(devenv) JPs-MacBook-Pro:argo-workflows jpzivalich$

I think it might be having a hard time installing things on my docker-desktop cluster
@isubasinghe - could you point me in the right direction?

[JPZ13]

On our call yesterday @rohankmr414 had a question about adding the dependency files. Rohan, could you ask it here?

[isubasinghe]

I should have probably mentioned this before, but this does assume kubernetes related stuff has been setup.

[JPZ13]

@isubasinghe and I hopped on a call today and were able to get my issue sorted. All I had to do was restart the terminal after installing nix rather than just opening up a new tab on iterm 🤷‍♂️

[JPZ13]

Looks good! 🚀

I had to delete my .devenv folder after pulling the new commits, but after deleting and refreshing, it worked great