refactor: 프로퍼티 권한 private -> protected 변경

closed #60

server/src/main/java/com/ticketing/server/global/dto/repository/AbstractEntity.java

@@ -19,15 +19,15 @@ public abstract class AbstractEntity {
 
 	@Id
 	@GeneratedValue(strategy = GenerationType.IDENTITY)
-	private Long id;
+	protected Long id;
 
 	@Column(nullable = false, updatable = false)
 	@CreatedDate
-	private LocalDateTime createdAt;
+	protected LocalDateTime createdAt;
 
 	@LastModifiedDate
-	private LocalDateTime updatedAt;
+	protected LocalDateTime updatedAt;
 
-	private LocalDateTime deletedAt;
+	protected LocalDateTime deletedAt;
 
 }