OpenAPI: Go to OpenAPI/Swagger generator

[manusa]

Description

Part of #6130

The OpenAPI spec published by Kubernetes or by the cluster (kubectl get --raw /openapi/v2) lacks model for some types. These types are those used in webhooks, types for the representation of the .kube/config file, and types used in common extensions (metrics server, gateway-api, and so on).

To be able to generate the Java types using the new OpenAPI approach, we still need some mechanism to extract these specifications from the Go types and structs.

Specifications

• Implement a new Go module in kubernetes-model-generator/openapi/generator:
  module github.com/fabric8io/kubernetes-client/kubernetes-model-generator/openapi/generator
• Implement a CLI that accepts a single parameter to specify the output directory of the generated OpenAPI specs
  $ generator ./output
• Generated APIs (more can be added later)

  Name	Description
  kubernetes-config.json	Types used in the Kubernetes configuration file (.kube/config)
  api-machinery-extra.json	Additional types in apimachinery not directory exposed in swagger.json
  admission-registration.json	Webhooks for this group
  gateway-api.json	https://github.com/kubernetes-sigs/gateway-api
  kustomize.json	https://github.com/kubernetes-sigs/kustomize
  metrics-server.json	https://github.com/kubernetes-sigs/metrics-server

Implementation tasks and PRs

These are some of the bits that have already been implemented as part of the work done for #6080.

• feat: Kubernetes types to OpenAPI generator #6113
• fix: add support for MicroTime in openapi generator #6116
• feat: improve openapi generator support for apiextensions #6117
• fix: add support for request options in openapi generator #6118
• fix: add support for Pod exec options in openapi generator #6119
• fix: add temp support for TypeMeta in openapi generator #6120
• fix: add support for AdmissionRequest in openapi generator #6121
• fix: add support for JSONSchemaProps in openapi generator #6122
• feat: openapi generator generates fake paths #6124
• feat: openapi generator generates reference grant #6125
• feat: openapi generator generates kustomize #6126
• feat: openapi generator generates metrics #6127