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/go/model_user.go

@@ -0,0 +1,31 @@
+/*
+ * 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 petstoreserver
+
+// User - A User who is purchasing from the pet store
+type User struct {
+
+	Id int64 `json:"id,omitempty"`
+
+	Username string `json:"username,omitempty"`
+
+	FirstName string `json:"firstName,omitempty"`
+
+	LastName string `json:"lastName,omitempty"`
+
+	Email string `json:"email,omitempty"`
+
+	Password string `json:"password,omitempty"`
+
+	Phone string `json:"phone,omitempty"`
+
+	// User Status
+	UserStatus int32 `json:"userStatus,omitempty"`
+}