feat(content-ranking): 오디오 랭킹 응답 계약을 추가한다

src/main/kotlin/kr/co/vividnext/sodalive/v2/api/content/ranking/dto/AudioRankingResponse.kt

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+package kr.co.vividnext.sodalive.v2.api.content.ranking.dto
+
+import com.fasterxml.jackson.annotation.JsonProperty
+import kr.co.vividnext.sodalive.v2.content.ranking.domain.AudioRanking
+import kr.co.vividnext.sodalive.v2.content.ranking.domain.AudioRankingItem
+import kr.co.vividnext.sodalive.v2.content.ranking.domain.AudioRankingType
+
+data class AudioRankingResponse(
+    val showRankChange: Boolean,
+    val type: AudioRankingType,
+    val items: List<AudioRankingItemResponse>
+) {
+    companion object {
+        fun from(ranking: AudioRanking): AudioRankingResponse {
+            return AudioRankingResponse(
+                showRankChange = ranking.showRankChange,
+                type = ranking.type,
+                items = ranking.items.map(AudioRankingItemResponse::from)
+            )
+        }
+    }
+}
+
+data class AudioRankingItemResponse(
+    val contentId: Long,
+    val title: String,
+    val creatorNickname: String,
+    val rank: Int,
+    val rankChange: Int?,
+    @JsonProperty("isNew")
+    val isNew: Boolean,
+    val coverImageUrl: String?
+) {
+    companion object {
+        fun from(item: AudioRankingItem): AudioRankingItemResponse {
+            return AudioRankingItemResponse(
+                contentId = item.contentId,
+                title = item.title,
+                creatorNickname = item.creatorNickname,
+                rank = item.rank,
+                rankChange = item.rankChange,
+                isNew = item.isNew,
+                coverImageUrl = item.coverImageUrl
+            )
+        }
+    }
+}

src/main/kotlin/kr/co/vividnext/sodalive/v2/content/ranking/domain/AudioRanking.kt

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+package kr.co.vividnext.sodalive.v2.content.ranking.domain
+
+data class AudioRanking(
+    val showRankChange: Boolean,
+    val type: AudioRankingType,
+    val items: List<AudioRankingItem>
+)
+
+data class AudioRankingItem(
+    val contentId: Long,
+    val title: String,
+    val creatorNickname: String,
+    val rank: Int,
+    val rankChange: Int?,
+    val isNew: Boolean,
+    val coverImageUrl: String?
+)

src/main/kotlin/kr/co/vividnext/sodalive/v2/content/ranking/domain/AudioRankingType.kt

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+package kr.co.vividnext.sodalive.v2.content.ranking.domain
+
+enum class AudioRankingType {
+    WEEKLY_POPULAR,
+    RISING,
+    REVENUE,
+    SALES_COUNT,
+    COMMENT_COUNT,
+    LIKE_COUNT
+}

src/test/kotlin/kr/co/vividnext/sodalive/v2/api/content/ranking/dto/AudioRankingResponseTest.kt

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+package kr.co.vividnext.sodalive.v2.api.content.ranking.dto
+
+import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper
+import kr.co.vividnext.sodalive.v2.content.ranking.domain.AudioRanking
+import kr.co.vividnext.sodalive.v2.content.ranking.domain.AudioRankingItem
+import kr.co.vividnext.sodalive.v2.content.ranking.domain.AudioRankingType
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.DisplayName
+import org.junit.jupiter.api.Test
+
+class AudioRankingResponseTest {
+    private val objectMapper = jacksonObjectMapper()
+
+    @Test
+    @DisplayName("오디오 랭킹 도메인을 응답 DTO로 변환하고 isNew JSON 필드명을 유지한다")
+    fun shouldMapAudioRankingToResponseAndSerializeIsNew() {
+        val ranking = AudioRanking(
+            showRankChange = true,
+            type = AudioRankingType.RISING,
+            items = listOf(
+                AudioRankingItem(
+                    contentId = 1001L,
+                    title = "rising audio",
+                    creatorNickname = "creator",
+                    rank = 1,
+                    rankChange = 3,
+                    isNew = true,
+                    coverImageUrl = "https://cdn.test/audio.png"
+                )
+            )
+        )
+
+        val response = AudioRankingResponse.from(ranking)
+        val json = objectMapper.readTree(objectMapper.writeValueAsString(response))
+
+        assertEquals(true, response.showRankChange)
+        assertEquals(AudioRankingType.RISING, response.type)
+        assertEquals(1001L, response.items[0].contentId)
+        assertEquals("rising audio", response.items[0].title)
+        assertEquals("creator", response.items[0].creatorNickname)
+        assertEquals(1, response.items[0].rank)
+        assertEquals(3, response.items[0].rankChange)
+        assertEquals(true, response.items[0].isNew)
+        assertEquals("https://cdn.test/audio.png", response.items[0].coverImageUrl)
+        assertEquals(true, json["items"][0]["isNew"].asBoolean())
+        assertEquals(false, json["items"][0].has("new"))
+    }
+}