feat: make preview_image_url nullable across post-related DTOs and database schema

backend/feature/post/src/adapter/delivery/create_post_request_dto.rs

@@ -12,8 +12,8 @@ pub struct CreatePostRequestDto {
     pub content: String,
     pub label_ids: Vec<i32>,
 
-    #[schema(format = Uri)]
-    pub preview_image_url: String,
+    #[schema(required, format = Uri)]
+    pub preview_image_url: Option<String>,
 
     #[schema(required, format = DateTime)]
     pub published_time: Option<String>,

backend/feature/post/src/adapter/delivery/post_info_response_dto.rs

@@ -14,7 +14,7 @@ pub struct PostInfoResponseDto {
     pub labels: Vec<LabelResponseDto>,
 
     #[schema(format = Uri)]
-    pub preview_image_url: String,
+    pub preview_image_url: Option<String>,
 
     #[schema(format = DateTime)]
     pub published_time: Option<String>,

backend/feature/post/src/adapter/delivery/update_post_request_dto.rs

@@ -12,8 +12,8 @@ pub struct UpdatePostRequestDto {
     pub content: String,
     pub label_ids: Vec<i32>,
 
-    #[schema(format = Uri)]
-    pub preview_image_url: String,
+    #[schema(required, format = Uri)]
+    pub preview_image_url: Option<String>,
 
     #[schema(required, format = DateTime)]
     pub published_time: Option<String>,

backend/feature/post/src/adapter/gateway/post_info_db_mapper.rs

@@ -7,7 +7,7 @@ pub struct PostInfoMapper {
     pub semantic_id: String,
     pub title: String,
     pub description: String,
-    pub preview_image_url: String,
+    pub preview_image_url: Option<String>,
     pub published_time: Option<NaiveDateTime>,
     pub labels: Vec<LabelMapper>,
 }

backend/feature/post/src/domain/entity/post_info.rs

@@ -10,7 +10,7 @@ pub struct PostInfo {
     pub semantic_id: String,
     pub title: String,
     pub description: String,
-    pub preview_image_url: String,
+    pub preview_image_url: Option<String>,
     pub labels: Vec<Label>,
     pub published_time: Option<DateTime<Utc>>,
 }

backend/feature/post/src/framework/db/post_info_with_label_record.rs

@@ -6,7 +6,7 @@ pub struct PostInfoWithLabelRecord {
     pub semantic_id: String,
     pub title: String,
     pub description: String,
-    pub preview_image_url: String,
+    pub preview_image_url: Option<String>,
     pub published_time: Option<NaiveDateTime>,
 
     pub label_id: Option<i32>,

backend/feature/post/src/framework/db/post_with_label_record.rs

@@ -6,7 +6,7 @@ pub struct PostWithLabelRecord {
     pub semantic_id: String,
     pub title: String,
     pub description: String,
-    pub preview_image_url: String,
+    pub preview_image_url: Option<String>,
     pub content: String,
     pub published_time: Option<NaiveDateTime>,
 

backend/migrations/20251014133149_make_preview_image_url_nullable.down.sql

@@ -0,0 +1,2 @@
+-- Revert post.preview_image_url to NOT NULL
+ALTER TABLE "post" ALTER COLUMN "preview_image_url" SET NOT NULL;

backend/migrations/20251014133149_make_preview_image_url_nullable.sql

@@ -0,0 +1,2 @@
+-- Make post.preview_image_url nullable
+ALTER TABLE "post" ALTER COLUMN "preview_image_url" DROP NOT NULL;

frontend/src/lib/post/adapter/gateway/creatPostRequestDto.ts

@@ -6,7 +6,7 @@ export class CreatePostRequestDto {
 	readonly description: string;
 	readonly content: string;
 	readonly labelIds: number[];
-	readonly previewImageUrl: URL;
+	readonly previewImageUrl: URL | null;
 	readonly publishedTime: Date | null;
 
 	private constructor(props: {
@@ -15,7 +15,7 @@ export class CreatePostRequestDto {
 		description: string;
 		content: string;
 		labelIds: number[];
-		previewImageUrl: URL;
+		previewImageUrl: URL | null;
 		publishedTime: Date | null;
 	}) {
 		this.semanticId = props.semanticId;
@@ -33,7 +33,7 @@ export class CreatePostRequestDto {
 			description: '',
 			content: '',
 			labelIds: [],
-			previewImageUrl: new URL('https://example.com'),
+			previewImageUrl: null,
 			publishedTime: null,
 		});
 	}

frontend/src/lib/post/adapter/gateway/postInfoResponseDto.ts

@@ -7,7 +7,7 @@ export const PostInfoResponseSchema = z.object({
 	semantic_id: z.string(),
 	title: z.string(),
 	description: z.string(),
-	preview_image_url: z.url(),
+	preview_image_url: z.url().nullable(),
 	labels: z.array(LabelResponseSchema),
 	published_time: z.iso.datetime({ offset: true }).nullable(),
 });
@@ -17,7 +17,7 @@ export class PostInfoResponseDto {
 	readonly semanticId: string;
 	readonly title: string;
 	readonly description: string;
-	readonly previewImageUrl: URL;
+	readonly previewImageUrl: URL | null;
 	readonly labels: readonly LabelResponseDto[];
 	readonly publishedTime: Date | null;
 
@@ -26,7 +26,7 @@ export class PostInfoResponseDto {
 		semanticId: string;
 		title: string;
 		description: string;
-		previewImageUrl: URL;
+		previewImageUrl: URL | null;
 		labels: LabelResponseDto[];
 		publishedTime: Date | null;
 	}) {
@@ -47,12 +47,17 @@ export class PostInfoResponseDto {
 			published_time = new Date(parsedJson.published_time);
 		}
 
+		let preview_image_url: URL | null = null;
+		if (parsedJson.preview_image_url !== null) {
+			preview_image_url = new URL(parsedJson.preview_image_url);
+		}
+
 		return new PostInfoResponseDto({
 			id: parsedJson.id,
 			semanticId: parsedJson.semantic_id,
 			title: parsedJson.title,
 			description: parsedJson.description,
-			previewImageUrl: new URL(parsedJson.preview_image_url),
+			previewImageUrl: preview_image_url,
 			labels: parsedJson.labels.map((label) => LabelResponseDto.fromJson(label)),
 			publishedTime: published_time,
 		});

frontend/src/lib/post/adapter/presenter/postInfoViewModel.ts

@@ -9,7 +9,7 @@ export class PostInfoViewModel {
 	readonly semanticId: string;
 	readonly title: string;
 	readonly description: string;
-	readonly previewImageUrl: URL;
+	readonly previewImageUrl: URL | null;
 	readonly labels: readonly LabelViewModel[];
 	readonly publishedTime: Date | null;
 
@@ -18,7 +18,7 @@ export class PostInfoViewModel {
 		semanticId: string;
 		title: string;
 		description: string;
-		previewImageUrl: URL;
+		previewImageUrl: URL | null;
 		labels: readonly LabelViewModel[];
 		publishedTime: Date | null;
 	}) {
@@ -49,12 +49,17 @@ export class PostInfoViewModel {
 			publishedTime = new Date(props.publishedTime);
 		}
 
+		let previewImageUrl: URL | null = null;
+		if (props.previewImageUrl) {
+			previewImageUrl = new URL(props.previewImageUrl);
+		}
+
 		return new PostInfoViewModel({
 			id: props.id,
 			semanticId: props.semanticId,
 			title: props.title,
 			description: props.description,
-			previewImageUrl: new URL(props.previewImageUrl),
+			previewImageUrl: previewImageUrl,
 			labels: props.labels.map((label) => LabelViewModel.rehydrate(label)),
 			publishedTime: publishedTime,
 		});
@@ -74,7 +79,7 @@ export class PostInfoViewModel {
 			semanticId: this.semanticId,
 			title: this.title,
 			description: this.description,
-			previewImageUrl: this.previewImageUrl.href,
+			previewImageUrl: this.previewImageUrl?.href ?? null,
 			labels: this.labels.map((label) => label.dehydrate()),
 			publishedTime: this.publishedTime?.getTime() ?? null,
 		};
@@ -86,7 +91,7 @@ export interface DehydratedPostInfoProps {
 	semanticId: string;
 	title: string;
 	description: string;
-	previewImageUrl: string;
+	previewImageUrl: string | null;
 	labels: DehydratedLabelProps[];
 	publishedTime: number | null;
 }

frontend/src/lib/post/domain/entity/postInfo.ts

@@ -5,7 +5,7 @@ export class PostInfo {
 	readonly semanticId: string;
 	readonly title: string;
 	readonly description: string;
-	readonly previewImageUrl: URL;
+	readonly previewImageUrl: URL | null;
 	readonly labels: readonly Label[];
 	readonly publishedTime: Date | null;
 
@@ -14,7 +14,7 @@ export class PostInfo {
 		semanticId: string;
 		title: string;
 		description: string;
-		previewImageUrl: URL;
+		previewImageUrl: URL | null;
 		labels: readonly Label[];
 		publishedTime: Date | null;
 	}) {

frontend/src/lib/post/framework/ui/PostContentPage.svelte

@@ -14,27 +14,28 @@
 
 	const md = markdownit();
 	const parsedContent = $derived(state.data?.content ? md.render(state.data.content) : '');
+	const postInfo = $derived(state.data?.info);
 
 	onMount(() => postBloc.dispatch({ event: PostEventType.PostLoadedEvent, id: id }));
 </script>
 
 <svelte:head>
-	<title>{generateTitle(state.data?.info.title)}</title>
-	{#if state.data}
-		<meta name="description" content={state.data.info.description} />
-		{#if state.data.info.isPublished}
+	<title>{generateTitle(postInfo?.title)}</title>
+	{#if postInfo}
+		<meta name="description" content={postInfo.description} />
+		{#if postInfo.isPublished}
 			<StructuredData
-				headline={state.data.info.title}
-				description={state.data.info.description}
-				datePublished={state.data.info.publishedTime!}
-				image={state.data.info.previewImageUrl}
+				headline={postInfo.title}
+				description={postInfo.description}
+				datePublished={postInfo.publishedTime!}
+				image={postInfo.previewImageUrl}
 			/>
 		{/if}
 	{/if}
 </svelte:head>
-<article class="content-container prose pb-10 prose-gray">
-	{#if state.data}
-		<PostContentHeader postInfo={state.data.info} />
+<article class="content-container prose prose-gray pb-10">
+	{#if postInfo}
+		<PostContentHeader {postInfo} />
 		<div class="max-w-3xl">
 			<hr />
 			<SafeHtml html={parsedContent} />

frontend/src/lib/post/framework/ui/PostPreview.svelte

@@ -7,11 +7,11 @@
 	let isImageLoading = $state(true);
 	let isImageError = $state(false);
 
-	function handleImageLoad() {
+	function onImageLoad() {
 		isImageLoading = false;
 	}
 
-	function handleImageError() {
+	function onImageError() {
 		isImageLoading = false;
 		isImageError = true;
 	}
@@ -27,10 +27,10 @@
 			class="rounded-2xl object-cover transition-opacity duration-300
                 {isImageLoading ? 'opacity-0' : 'opacity-100'}
                 {isImageError ? 'hidden' : ''}"
-			src={postInfo.previewImageUrl.href}
+			src={postInfo.previewImageUrl?.href}
 			alt={postInfo.title}
-			onload={handleImageLoad}
-			onerror={handleImageError}
+			onload={onImageLoad}
+			onerror={onImageError}
 		/>
 		{#if isImageLoading || isImageError}
 			<div class="absolute inset-0 flex items-center justify-center bg-gray-200"></div>

frontend/src/lib/post/framework/ui/StructuredData.svelte

@@ -10,7 +10,7 @@
 		headline: string;
 		description: string;
 		datePublished: Date;
-		image: URL;
+		image: URL | null;
 	} = $props();
 
 	const structuredData = $derived({
@@ -19,7 +19,7 @@
 		headline: headline,
 		description: description,
 		datePublished: datePublished.toISOString(),
-		image: image.href,
+		image: image?.href,
 	});
 
 	const jsonLdScript = $derived(