feat: content query 추가

content-query/src/main/java/com/example/contentquery/service/ContentQueryService.java

@@ -0,0 +1,21 @@
+package com.example.contentquery.service;
+
+import com.example.contentquery.repository.Content;
+import com.example.contentquery.repository.ContentQueryRepository;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.stereotype.Service;
+
+@Service
+@RequiredArgsConstructor
+@Slf4j
+public class ContentQueryService {
+
+    private final ContentQueryRepository contentQueryRepository;
+
+    public Content findByPostId(Long contentId) {
+        return contentQueryRepository.findByContentId(contentId).orElseThrow(
+                () -> new RuntimeException("해당 게시글이 존재하지 않습니다.")
+        );
+    }
+}