extend Post entity with feature slot

Adds nullable feature_slot column (unique) plus repo
findByFeatureSlot/findFeatured/update methods so admins can
pin a post into one of two slots.

backend/app/Post/EloquentPostRepository.php

@@ -4,6 +4,7 @@ namespace App\Post;
 
 use DateTimeImmutable;
 use DateTimeZone;
+use RuntimeException;
 
 class EloquentPostRepository implements PostRepository
 {
@@ -65,6 +66,53 @@ class EloquentPostRepository implements PostRepository
         PostModel::query()->where('id', $id)->delete();
     }
 
+    /**
+     * @throws RuntimeException
+     */
+    public function update(Post $post): Post
+    {
+        $model = PostModel::find($post->getId());
+        if ($model === null) {
+            throw new RuntimeException(
+                "Post with id: {$post->getId()} does not exist"
+            );
+        }
+        $model->user_id = $post->getUserId();
+        $model->title = $post->getTitle();
+        $model->body = $post->getBody();
+        $model->created_at = $post->getCreatedAt();
+        $model->feature_slot = $post->getFeatureSlot();
+        $model->save();
+
+        return $this->toDomain($model);
+    }
+
+    public function findByFeatureSlot(int $slot): ?Post
+    {
+        $model = PostModel::query()
+            ->where('feature_slot', $slot)
+            ->first();
+
+        return $model === null ? null : $this->toDomain($model);
+    }
+
+    /**
+     * @return Post[]
+     */
+    public function findFeatured(): array
+    {
+        $models = PostModel::query()
+            ->whereNotNull('feature_slot')
+            ->orderBy('feature_slot', 'asc')
+            ->get();
+
+        return $models->map(
+            function (PostModel $model) {
+                return $this->toDomain($model);
+            },
+        )->all();
+    }
+
     private function toDomain(PostModel $model): Post
     {
         $utc = new DateTimeZone('UTC');
@@ -78,6 +126,7 @@ class EloquentPostRepository implements PostRepository
                 $model->created_at->toDateTimeString(),
                 $utc,
             ),
+            featureSlot: $model->feature_slot,
         );
     }
 }