fix: don't repeat join event

src/main.rs

@@ -125,6 +125,7 @@ async fn handle_ntfy(target: String, mut sub: broadcast::Receiver<session::Sessi
 	while let Ok(event) = sub.recv().await {
 		if let Err(e) = match event {
 			session::SessionEvent::AddUser(user) => {
+				if users.contains_key(&user.session) { continue }
 				users.insert(user.session, user.name.clone());
 				client
 					.post(&target)