Create Notification service struct skeleton.

src/controller/mod.rs

 pub mod product;
+pub mod notification;
 
 use rocket::fairing::AdHoc;
 
@@ -6,5 +7,6 @@ pub fn route_stage() -> AdHoc {
     return AdHoc::on_ignite("Initializing controller routes...", |rocket| async {
         rocket
             .mount("/product", routes![product::create, product::list, product::read, product::delete])
+            .mount("/notification", routes![])
     });
 }

src/controller/notification.rs

+use rocket::response::status::Created;
+use rocket::serde::json::Json;
+
+use bambangshop::Result;
+use crate::model::subscriber::Subscriber;
+use crate::service::notification::NotificationService;

src/service/mod.rs

 pub mod product;
+pub mod notification;
\ No newline at end of file

src/service/notification.rs

+use std::thread;
+use bambangshop::{Result, compose_error_response};
+use rocket::http::Status;
+use crate::model::notification::Notification;
+use crate::model::product::Product;
+use crate::model::subscriber::Subscriber;
+use crate::repository::subscriber::SubscriberRepository;
+
+pub struct NotificationService;
+
+impl NotificationService {
+}
\ No newline at end of file