Add post change log tracking

backend/src/main/java/com/openisle/dto/PostChangeLogDto.java

@@ -0,0 +1,30 @@
+package com.openisle.dto;
+
+import com.openisle.model.PostChangeType;
+import lombok.Getter;
+import lombok.Setter;
+
+import java.time.LocalDateTime;
+
+@Getter
+@Setter
+public class PostChangeLogDto {
+    private Long id;
+    private String username;
+    private PostChangeType type;
+    private LocalDateTime time;
+    private String oldTitle;
+    private String newTitle;
+    private String oldContent;
+    private String newContent;
+    private String oldCategory;
+    private String newCategory;
+    private String oldTags;
+    private String newTags;
+    private Boolean oldClosed;
+    private Boolean newClosed;
+    private LocalDateTime oldPinnedAt;
+    private LocalDateTime newPinnedAt;
+    private Boolean oldFeatured;
+    private Boolean newFeatured;
+}