Add a VS Code devcontainer configuration

[olix0r]

Motivation

When loading kube-rs in VS Code, a variety of configurations are
needed to end up with a working environment. It does't Just Work out of
the box.

Solution

VS Code devcontainers make it easy to bootstrap a development
environment with project-specific tooling and configuration. This
configuration should also be usable in GitHub Codespaces.

This configuration ensures that various tools are available including:

• cargo-deny
• cargo-tarpaulin
• k3d
• kubectl
• rust stable-1.56 toolchain
• rust nightly toolchain
• a few related VS Code plugins

While this developer image is based on rust 1.56 (the documented MSRV
for the project), it updates the default toolchain to be nightly so
clippy and rustfmt work as expected (since kube-rs depends on nightly
versions of these tools).

---

On one hand, I'd rather not commit configuration for any single editor into the repo. On the other hand, having a working development environment in VS Code should dramatically reduce the setup time for new contributors. We've recently adopted devcontainers in Linkerd (1 2), so I thought I'd share a modified version for kube-rs. At the very least, this would help me; but I won't be offended if this isn't accepted here.

Note that I've tried to omit anything touching developer-specific personalization (choice of shell, etc), leaving that to be configured in a dotfiles repo (eg) and in user-specific vscode configuration.

[clux]

I think this is great. Thanks a lot for contributing this.
Need to have a few days for some time to play around with it, but I am happy to merge this in if it helps people.

[clux]

left some comments + suggestions + questions after having tested out the basics + the extensions. definitely merging this as it's pretty easy to maintain and an easy win.

some overall questions:

i guess the way you intend to use this is by creating a new sh terminal inside the container and using make test etc in there? do you want to be able to run lldb against examples? presumably this is doable, but didn't get that far.

i would have assumed the builtin tasks would be useful for less terminal use, but not even sure they forward into the devcontainer (or if they can be configured at this level) - there's another comment on that.

[olix0r]

@clux

i guess the way you intend to use this is by creating a new sh terminal inside the container and using make test etc in there? do you want to be able to run lldb against examples? presumably this is doable, but didn't get that far.

i would have assumed the builtin tasks would be useful for less terminal use, but not even sure they forward into the devcontainer (or if they can be configured at this level) - there's another comment on that.

My workflow is generally to use a terminal to run compilations, etc (because RLS/compiling is painfully slow in Linkerd); but I should give tasks a shot in kube-rs. I'll take a look at configuring them.

Re: lldb, I didn't actually try it. I can remove that plugin for now. I think it was a recommended plugin for rust projects and I cargo-culted it here.

[clux]

I don't have any further comments on this. Are you happy with it as is?

[olix0r]

@clux I noticed a small issue with the dev container workflow, but fine to merge once the build is green :)

Thanks!