feat(home-following): 최근 소식 source key를 추가한다

src/main/kotlin/kr/co/vividnext/sodalive/v2/home/following/domain/HomeFollowingNewsSourceKey.kt

@@ -0,0 +1,17 @@
+package kr.co.vividnext.sodalive.v2.home.following.domain
+
+import java.time.LocalDateTime
+
+object HomeFollowingNewsSourceKey {
+    fun creatorRanking(creatorId: Long, aggregationStartAtUtc: LocalDateTime): String {
+        return "${FollowingNewsType.CREATOR_RANKING.name}:$creatorId:$aggregationStartAtUtc"
+    }
+
+    fun audioContent(contentId: Long): String {
+        return "${FollowingNewsType.AUDIO_CONTENT.name}:$contentId"
+    }
+
+    fun communityPost(postId: Long): String {
+        return "${FollowingNewsType.COMMUNITY_POST.name}:$postId"
+    }
+}