Can notify a player that the server is waiting for opponent play configuration

rust/sea_battle_backend/src/game.rs

@@ -22,6 +22,8 @@ pub trait Player {
 
     fn rejected_boats_layout(&self, errors: Vec<&'static str>);
 
+    fn waiting_for_opponent_boats_layout(&self);
+
     fn notify_other_player_ready(&self);
 
     fn notify_game_starting(&self);
@@ -294,6 +296,8 @@ impl Handler<SetBoatsLayout> for Game {
         if self.map_0.is_some() && self.map_1.is_some() {
             self.players.iter().for_each(|p| p.notify_game_starting());
             self.start_fire_exchanges();
+        } else {
+            self.players[player_index].waiting_for_opponent_boats_layout();
         }
     }
 }