Implementing OpenApi 3 specs (converted from Swagger 2) (#53243)

* Adding OpenApi target to makefile, to covert swagger spec into OpenAPI 3
* Adding endpoint to server swaggerui with new openapi3 specs
* Passing output file as parameter for OpenApi3 specs
* Implement workaround for missing host and prefix domain

scripts/openapi3/openapi3conv.go

@@ -0,0 +1,61 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"github.com/getkin/kin-openapi/openapi2"
+	"github.com/getkin/kin-openapi/openapi2conv"
+	"github.com/getkin/kin-openapi/openapi3"
+	"io/ioutil"
+	"os"
+)
+
+// main This simple script will take the swagger v2 spec generated by grafana and convert them into openapi 3
+// saving them as new json file to be able lo load and show
+// The first parameter, if present, will be the input file
+// The second parameter, if present, will be the output file
+func main() {
+	outFile := "public/openapi3.json"
+	inFile := "api-merged.json"
+	args := os.Args[1:]
+
+	// first parameter as the input
+	if len(args) > 0 && args[0] != "" {
+		inFile = args[0]
+	}
+
+	// second parameter as output
+	if len(args) > 1 && args[1] != "" {
+		outFile = args[1]
+	}
+
+	fmt.Printf("Reading swagger 2 file %s\n", inFile)
+	byt, err := ioutil.ReadFile(inFile)
+	if err != nil {
+		panic(err)
+	}
+
+	var doc2 openapi2.T
+	if err = json.Unmarshal(byt, &doc2); err != nil {
+		panic(err)
+	}
+
+	doc3, err := openapi2conv.ToV3(&doc2)
+	if err != nil {
+		panic(err)
+	}
+
+	// this is a workaround. In the swagger2 specs there ir no definition of the host, so the converter can not create
+	// a URL. Adding this will ensure that all the api calls start with "/api".
+	doc3.AddServer(&openapi3.Server{URL: "/api"})
+
+	j3, err := doc3.MarshalJSON()
+	if err != nil {
+		panic(err)
+	}
+
+	if err = ioutil.WriteFile(outFile, j3, 0644); err != nil {
+		panic(err)
+	}
+	fmt.Printf("OpenAPI specs generated in file %s\n", outFile)
+}