feat: mvp cuelang implementation

[lorenzofelletti]

Fixes #257

Proposed Changes

• Adding CUE-lang input. Allow to compile CUE modules and injecting values from Kapitan parameters.

Docs and Tests

• Tests added
• Updated documentation

[ademariag]

I've been meaning to do it for months! Thank you Lorenzo!

[lorenzofelletti]

This is an MVP of compiling CUE modules with Kapitan. It pretty much follows the Kustomize InputType implementation.

I've tested it locally by building the Docker image and testing it against a minimal project obtained by:

• creating a new folder and running kapitan init in it
• creating a folder templates/cue and running cue mod init com.cue.example from within that folder
• adding file templates/cue/main.cue with content below
• editing inventory/classes/my_component.yml and adding the content from below
• running kapitan compile (with kapitan aliased to the use the built image).

parameters:
  your_component:
    some_parameter: true
  kapitan:
    compile:
    - output_path: cute
      input_type: cuelang
      input_paths:
      - templates/cue
      input:
        some_input: true

main.cue:

package main

hello: "world"

[ademariag]

this is great @lorenzofelletti. Would you mind adding a little bit of documentation to the documentation site, and some tests?

Then I think we are ready to ship

[lorenzofelletti]

Yes, you're right! I'll add them!