feat: Use new go-based generator

[jedevc]

This removes our dependency on openapitools/openapi-generator-cli, which has a few issues:

• It's huge. Needing to pull this locally to generate the go code is annoying.
• The templating language is limited. This work was originally motivated by being unable to inject new functions for doing string casing for enums.

To do this, we adapt all the templates into golang, and do all the parsing in Go. It's a tidy ~1000 lines of Go to do all the parsing. We could do further simplifications as well, we'd need something like getkin/kin-openapi#695 to remove our weird reordering work.

The output is identical. The only difference now is that the generated files get .gen.go filenames, so that they can easily be marked in .gitattributes.

[Copilot]

Pull request overview

This PR replaces the dependency on openapitools/openapi-generator-cli with a custom Go-based code generator. The motivation is to eliminate a large dependency and overcome templating language limitations. The output is claimed to be identical, with the only difference being that generated files now use .gen.go filenames for easier identification in .gitattributes.

Changes:

• Implements a new Go-based OpenAPI code generator (~1000 lines) in tools/codegen/
• Converts Handlebars templates to Go templates with updated syntax
• Generates identical output but with .gen.go file extensions
• Removes dependency on Java-based OpenAPI generator tool

Reviewed changes

Copilot reviewed 37 out of 240 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tools/codegen/*.go	New Go-based generator implementation with parser, preprocessor, and template functions
tools/codegen/go.mod	Go module dependencies for the new generator
tools/codegen/templates/*.tmpl	Converted templates from Handlebars to Go template syntax
templates/*.handlebars	Deleted old Handlebars templates
platform/*.gen.go	Regenerated model files with new .gen.go extension
platform/.openapi-generator/VERSION	Removed as no longer using openapi-generator-cli

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[nderjung]

Can you please add the directory to templates as a flag option to the generator itself?

Such that:

- //go:generate go run -C ../tools/codegen . --input ../../controlplane.yaml --output ../../controlplane --package controlplane
+ //go:generate go run -C ../tools/codegen . --input ../../controlplane.yaml --output ../../controlplane --package controlplane --templates ../tools/codegen/templates

I believe @ajpetersons and @petar-cvit would benefit from being able to supply custom templates in separate external projects.

[nderjung]

It would also allow us to replace openapi-generator for other languages too actually.

Hmmm. Now I wonder if we should put this in unikraft.com/x/tools...

[jedevc]

As discussed offline, this is the eventual aim, so that we can support other SDKs and other codegen from openapi.

However, if we're doing that, the exact functions / data become part of an internal API. I'm not entirely sure I'm happy with the current state being exposed.

We could try and merge this as-is, and then later, we can pull this into x, and make templates fully configurable.

[craciunoiuc]

Maybe bump to the latest version hehe >:D

[craciunoiuc]

I trust this PR with my life

Reviewed-by: Cezar Craciunoiu cezar.craciunoiu@unikraft.com

[nderjung]

Thanks!

Approved-by: Alexander Jung alex@unikraft.com