Adds CORS protocol to server responses

Allow requests from all endpoints. Currently it is only running on
localhost.
It is required by the react's fetching lib used.

cmd/api-server/main.go

@@ -43,16 +43,26 @@ func main() {
 
 	// 3. HTTP server
 	e := echo.New()
+
+	// 3.1. logging
 	e.Use(middleware.Logger())
 
+	// 3.2. oapi validator
 	swagger, err := api.GetSwagger()
 	if err != nil {
 		log.Fatalf("unable to get API swagger: %v\n", err)
 	}
 	e.Use(echomiddleware.OapiRequestValidator(swagger))
 
+	// 3.3. CORS
+	e.Use(middleware.CORSWithConfig(middleware.CORSConfig{
+		AllowOrigins: []string{"*"},
+	}))
+
+	// 3.4. register implemented handlers
 	handlers := api.ServerImpl{Dal: &dal}
 	api.RegisterHandlers(e, &handlers)
 
+	// 3.5 run server
 	e.Logger.Fatal(e.Start(":9000"))
 }