make each handlers of CRUD API optional

gin.go

@@ -212,6 +212,8 @@ type Resource interface {
 	ReadHandler(*Context)
 	UpdateHandler(*Context)
 	DeleteHandler(*Context)
+
+	Supported(string) bool
 }
 
 // It defines
@@ -220,11 +222,22 @@ type Resource interface {
 //   PUT:  /path/:id
 //   POST: /path/:id
 func (group *RouterGroup) CRUD(path string, resource Resource) {
+	if resource.Supported("C") {
 		group.POST(path, resource.CreateHandler)
+	}
+
+	if resource.Supported("R") {
 		group.GET(path, resource.ReadHandler)
+	}
+
+	if resource.Supported("U") {
 		group.PUT(path+"/:id", resource.UpdateHandler)
+	}
+
+	if resource.Supported("D") {
 		group.DELETE(path+"/:id", resource.DeleteHandler)
 	}
+}
 
 // Static serves files from the given file system root.
 // Internally a http.FileServer is used, therefore http.NotFound is used instead