Generate API files as interfaces for go-gin server (#17784)

* add feature to generate only interface files

* generate sample

* add workflow file foe go gin service

* add workflow file foe go gin service

* add workflow file foe go gin service

* update samples

samples/server/petstore/go-gin-api-server-interface-only/main.go

@@ -0,0 +1,29 @@
+/*
+ * OpenAPI Petstore
+ *
+ * This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+ *
+ * API version: 1.0.0
+ * Generated by: OpenAPI Generator (https://openapi-generator.tech)
+ */
+
+package main
+
+import (
+	"log"
+
+	// WARNING!
+	// Pass --git-repo-id and --git-user-id properties when generating the code
+	//
+	sw "github.com/GIT_USER_ID/GIT_REPO_ID/go"
+)
+
+func main() {
+	routes := sw.ApiHandleFunctions{}
+
+	log.Printf("Server started")
+
+	router := sw.NewRouter(routes)
+
+	log.Fatal(router.Run(":8080"))
+}