CLAP-442 Feat : 작업 구분 null로 변경하는 logic 추가

Author: starboxxxx

src/main/java/clap/server/adapter/inbound/web/dto/task/request/UpdateTaskLabelRequest.java

@@ -6,7 +6,6 @@
 public record UpdateTaskLabelRequest(
 
         @Schema(description = "변경할 구분 고유 ID", example = "1")
-        @NotNull
         Long labelId
 ) {
 }

src/main/java/clap/server/application/service/task/UpdateTaskContentService.java

@@ -96,7 +96,7 @@ public void updateTaskLabel(Long taskId, Long memberId, UpdateTaskLabelRequest r
         memberService.findActiveMember(memberId);
         memberService.findReviewer(memberId);
         Task task = taskService.findById(taskId);
-        Label label = labelService.findById(request.labelId());
+        Label label = request.labelId() != null ? labelService.findById(request.labelId()) : null;
 
         task.updateLabel(label);
         taskService.upsert(task);