add contest announcement

contest/views/oj.py

@@ -0,0 +1,16 @@
+from utils.api import APIView
+
+from ..models import ContestAnnouncement
+from ..serializers import ContestAnnouncementSerializer
+
+
+class ContestAnnouncementListAPI(APIView):
+    def get(self, request):
+        contest_id = request.GET.get("contest_id")
+        if not contest_id:
+            return self.error("Invalid parameter")
+        data = ContestAnnouncement.objects.filter(contest_id=contest_id).order_by("-create_time")
+        max_id = request.GET.get("max_id")
+        if max_id:
+            data = data.filter(id__gt=max_id)
+        return self.success(ContestAnnouncementSerializer(data, many=True).data)