refactor: OrderCreatedEvent가 상세 정보를 스스로 포함하도록 개선

- 이벤트 리스너의 외부 서비스 의존성 제거 (Decoupling)
- 이벤트 객체가 발생 시점의 상태(재고)를 온전히 표현하도록 수정
- 비동기 처리 시 발생할 수 있는 데이터 불일치 가능성 방지

Author: yeonjiyeon

apps/commerce-api/src/main/java/com/loopers/application/order/OrderFacade.java

@@ -67,6 +67,7 @@ public OrderInfo placeOrder(PlaceOrder command) {
         order.getId(),
         user,
         orderItems,
+        products,
         finalPaymentAmount,
         command.paymentType(),
         command.cardType(),

apps/commerce-api/src/main/java/com/loopers/application/order/event/OrderCreatedEvent.java

@@ -2,9 +2,12 @@
 
 import com.loopers.domain.order.OrderItem;
 import com.loopers.domain.payment.PaymentType;
+import com.loopers.domain.product.Product;
 import com.loopers.domain.user.User;
 import java.util.List;
+import java.util.Map;
 import java.util.UUID;
+import java.util.stream.Collectors;
 
 public record OrderCreatedEvent(
     String eventId,
@@ -18,24 +21,31 @@ public record OrderCreatedEvent(
     Long couponId
 ) {
 
-  public record OrderItemInfo(Long productId, int quantity) {
+  public record OrderItemInfo(Long productId, int quantity, int remainStock) {
 
   }
 
   public static OrderCreatedEvent of(
       Long orderId,
       User user,
       List<OrderItem> orderItems,
+      List<Product> products,
       long finalAmount,
       PaymentType paymentType,
       String cardType,
       String cardNo,
       Long couponId
   ) {
 
+    Map<Long, Integer> stockMap = products.stream()
+        .collect(Collectors.toMap(Product::getId, Product::getStock));
+
     List<OrderItemInfo> itemInfos = orderItems.stream()
-        .map(item -> new OrderItemInfo(item.getProductId(), item.getQuantity()))
-        .toList();
+        .map(item -> new OrderItemInfo(
+            item.getProductId(),
+            item.getQuantity(),
+            stockMap.getOrDefault(item.getProductId(), 0)
+            )).toList();
 
     return new OrderCreatedEvent(
         UUID.randomUUID().toString(),

apps/commerce-api/src/main/java/com/loopers/application/order/event/OrderSalesAggregateListener.java

@@ -14,7 +14,6 @@
 @RequiredArgsConstructor
 public class OrderSalesAggregateListener {
 
-  private final ProductService productService;
   private final OutboxService outboxService;
   private final ApplicationEventPublisher eventPublisher;
 
@@ -24,11 +23,10 @@ public void handleOrderCreated(OrderCreatedEvent event) {
 
     event.items().forEach(item -> {
 
-      int currentStock = productService.getStock(item.productId());
       ProductStockEvent kafkaEvent = ProductStockEvent.of(
           item.productId(),
           item.quantity(),
-          currentStock
+          item.remainStock()
       );
 
       outboxService.saveEvent("STOCKS_METRICS", String.valueOf(item.productId()), kafkaEvent);