fixed stock entity key

backend/src/main/java/com/example/todoapp/dto/StockDTO.java

@@ -18,7 +18,7 @@ import java.time.LocalDate;
 @Data
 public class StockDTO {
     private int stock_id;
-    private Stuffs stuffs;
+    private int stuff_id;
     private Long user_id;
     private int amount;
     private int price;
@@ -35,7 +35,7 @@ public class StockDTO {
     public static StockDTO fromEntity(Stocks stock) {
         StockDTO dto = new StockDTO();
         dto.setStock_id(stock.getStock_id());
-        dto.setStuffs(stock.getStuffs());
+        dto.setStuff_id(stock.getStuff_id());
         dto.setUser_id(stock.getUser_id().getId());
         dto.setAmount(stock.getAmount());
         dto.setPrice(stock.getPrice());

backend/src/main/java/com/example/todoapp/model/Stocks.java

@@ -52,7 +52,7 @@ public class Stocks {
          referencedColumnName = "stuff_id",
          nullable = false
      )
-     private Stuffs stuffs;
+     private int stuff_id;
 
 
     /**