feat(model): add initial entity models for restaurant system

src/main/java/dev/model/MenuItem.java

@@ -0,0 +1,15 @@
+package dev.model;
+
+public class MenuItem {
+
+    private int id;
+
+    private String name;
+
+    private String description;
+
+    private double price;
+
+    private String category;
+
+}

src/main/java/dev/model/Order.java

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+package dev.model;
+
+import java.time.LocalDateTime;
+
+public class Order {
+
+    private int id;
+
+    private int userId;
+
+    private LocalDateTime createdAt;
+
+    private double totalPrice;
+
+}

src/main/java/dev/model/OrderDetail.java

@@ -0,0 +1,15 @@
+package dev.model;
+
+public class OrderDetail {
+
+    private int id;
+
+    private int orderId;
+
+    private int menuItemId;
+
+    private int quantity;
+
+    private double price;
+
+}

src/main/java/dev/model/User.java

@@ -0,0 +1,13 @@
+package dev.model;
+
+public class User {
+
+    private int id;
+
+    private String username;
+
+    private String password;
+
+    private String email;
+
+}