feat: add User entity and Role enum

src/main/java/com/example/bankcards/entity/Role.java

@@ -0,0 +1,6 @@
+package com.example.bankcards.entity;
+
+public enum Role {
+  ROLE_USER,
+  ROLE_ADMIN
+}

src/main/java/com/example/bankcards/entity/User.java

@@ -0,0 +1,65 @@
+package com.example.bankcards.entity;
+
+import jakarta.persistence.*;
+
+@Entity
+@Table(name = "users")
+public class User {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    @Column(nullable = false, unique = true)
+    private String username;
+
+    @Column(nullable = false)
+    private String password;
+
+    @Column(nullable = false, unique = true)
+    private String email;
+
+    @Enumerated(EnumType.STRING)
+    @Column(nullable = false)
+    private Role role;
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getUsername() {
+        return username;
+    }
+
+    public void setUsername(String username) {
+        this.username = username;
+    }
+
+    public String getPassword() {
+        return password;
+    }
+
+    public void setPassword(String password) {
+        this.password = password;
+    }
+
+    public String getEmail() {
+        return email;
+    }
+
+    public void setEmail(String email) {
+        this.email = email;
+    }
+
+    public Role getRole() {
+        return role;
+    }
+
+    public void setRole(Role role) {
+        this.role = role;
+    }
+}