openapi: Create client -> TypeConverter function

Allows creating a typeconverter from a client (i.e. by taking the data
of the client and formatting it so that one can create a type
converter).

staging/src/k8s.io/client-go/openapi/typeconverter.go

@@ -0,0 +1,48 @@
+/*
+Copyright 2023 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package openapi
+
+import (
+	"encoding/json"
+	"fmt"
+
+	"k8s.io/apimachinery/pkg/util/managedfields"
+	"k8s.io/kube-openapi/pkg/spec3"
+	"k8s.io/kube-openapi/pkg/validation/spec"
+)
+
+func NewTypeConverter(client Client, preserveUnknownFields bool) (managedfields.TypeConverter, error) {
+	spec := map[string]*spec.Schema{}
+	paths, err := client.Paths()
+	if err != nil {
+		return nil, fmt.Errorf("failed to list paths: %w", err)
+	}
+	for _, gv := range paths {
+		s, err := gv.Schema("application/json")
+		if err != nil {
+			return nil, fmt.Errorf("failed to download schema: %w", err)
+		}
+		var openapi spec3.OpenAPI
+		if err := json.Unmarshal(s, &openapi); err != nil {
+			return nil, fmt.Errorf("failed to parse schema: %w", err)
+		}
+		for k, v := range openapi.Components.Schemas {
+			spec[k] = v
+		}
+	}
+	return managedfields.NewTypeConverter(spec, preserveUnknownFields)
+}