redis cache manager - serializeKeysWith 추가

src/main/kotlin/kr/co/vividnext/sodalive/content/AudioContentController.kt

@@ -155,7 +155,7 @@ class AudioContentController(private val service: AudioContentService) {
     @GetMapping("/ranking")
     fun getAudioContentRanking(
         @AuthenticationPrincipal(expression = "#this == 'anonymousUser' ? null : member") member: Member?,
-        @RequestParam("sortType") sortType: String,
+        @RequestParam("sortType", required = false) sortType: String = "매출",
         pageable: Pageable
     ) = run {
         if (member == null) throw SodaException("로그인 정보를 확인해주세요.")