Support scripting KRM functions

[guettli]

Eschewed features

• This issue is not requesting templating, unstuctured edits, build-time side-effects from args or env vars, or any other eschewed feature.

What would you like to have added?

It would be great, if kustomize would include a scripting language for writing KRM functions.

These languages have a pure Go implementation: JS, starlark, Lua, cue.

Of course I could use Containerized KRM Functions but somehow an embedded language would feel more natural and lightweight to me.

Additionally, in air gapped environments it might be not possible to execute a container.

Why is this needed?

Sometimes I would like to do modifications which are not possible with an existing transformer.

Can you accomplish the motivating task without this feature, and if so, how?

I could use a Containerized KRM Functions.

What other solutions have you considered?

I could use Exec and a Bash script.

Anything else we should know?

Thank you for kustomize!

Feature ownership

• I am interested in contributing this feature myself! 🎉

[k8s-ci-robot]

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