Feat: 썸네일 DTO 및 Swagger 문서 추가 수정

Author: joyewon0705

src/main/java/com/back/domain/board/post/controller/PostControllerDocs.java

@@ -48,6 +48,7 @@ public interface PostControllerDocs {
                                         },
                                         "title": "첫 번째 게시글",
                                         "content": "안녕하세요, 첫 글입니다!",
+                                        "thumbnailUrl": null,
                                         "categories": [
                                           { "id": 1, "name": "공지사항" },
                                           { "id": 2, "name": "자유게시판" }
@@ -174,6 +175,7 @@ ResponseEntity<RsData<PostResponse>> createPost(
                                             "postId": 1,
                                             "author": { "id": 10, "nickname": "홍길동", "profileImageUrl": null },
                                             "title": "첫 글",
+                                            "thumbnailUrl": null,
                                             "categories": [{ "id": 1, "name": "공지사항" }],
                                             "likeCount": 5,
                                             "bookmarkCount": 2,
@@ -251,6 +253,7 @@ ResponseEntity<RsData<PageResponse<PostListResponse>>> getPosts(
                                         "author": { "id": 5, "nickname": "홍길동", "profileImageUrl": null },
                                         "title": "첫 번째 게시글",
                                         "content": "안녕하세요, 첫 글입니다!",
+                                        "thumbnailUrl": null,
                                         "categories": [
                                           { "id": 1, "name": "공지사항" },
                                           { "id": 2, "name": "자유게시판" }
@@ -327,6 +330,7 @@ ResponseEntity<RsData<PostDetailResponse>> getPost(
                                         },
                                         "title": "수정된 게시글",
                                         "content": "안녕하세요, 수정했습니다!",
+                                        "thumbnailUrl": null,
                                         "categories": [
                                           { "id": 1, "name": "공지사항" },
                                           { "id": 2, "name": "자유게시판" }

src/main/java/com/back/domain/board/post/dto/PostDetailResponse.java

@@ -25,6 +25,7 @@ public record PostDetailResponse(
         AuthorResponse author,
         String title,
         String content,
+        String thumbnailUrl,
         List<CategoryResponse> categories,
         long likeCount,
         long bookmarkCount,
@@ -44,6 +45,7 @@ public static PostDetailResponse from(Post post, boolean likedByMe, boolean book
                 AuthorResponse.from(post.getUser()),
                 post.getTitle(),
                 post.getContent(),
+                post.getThumbnailUrl(),
                 post.getCategories().stream()
                         .map(CategoryResponse::from)
                         .toList(),

src/main/java/com/back/domain/board/post/dto/PostResponse.java

@@ -21,6 +21,7 @@ public record PostResponse(
         AuthorResponse author,
         String title,
         String content,
+        String thumbnailUrl,
         List<CategoryResponse> categories,
         LocalDateTime createdAt,
         LocalDateTime updatedAt
@@ -31,6 +32,7 @@ public static PostResponse from(Post post) {
                 AuthorResponse.from(post.getUser()),
                 post.getTitle(),
                 post.getContent(),
+                post.getThumbnailUrl(),
                 post.getCategories().stream()
                         .map(CategoryResponse::from)
                         .toList(),