시리즈 콘텐츠 리스트 정렬

- required = false 대신 defaultValue를 이용하여 기본값 설정

src/main/kotlin/kr/co/vividnext/sodalive/content/series/ContentSeriesController.kt

@@ -50,7 +50,7 @@ class ContentSeriesController(private val service: ContentSeriesService) {
     @GetMapping("/{id}/content")
     fun getSeriesContentList(
         @PathVariable id: Long,
-        @RequestParam("sortType", required = false) sortType: SeriesSortType = SeriesSortType.NEWEST,
+        @RequestParam("sortType", defaultValue = "NEWEST") sortType: SeriesSortType,
         @AuthenticationPrincipal(expression = "#this == 'anonymousUser' ? null : member") member: Member?,
         pageable: Pageable
     ) = run {