feat(problemset): 用户奖章接口带出所属题单

成就页的奖章列表只有奖章本身，看不出来自哪个题单。UserBadgeSerializer
补一个 problemset 字段，查询改 select_related("badge__problemset") —— 这是
异步视图，不预加载会在异步上下文里发同步查询。

problemset/serializers.py

@@ -287,11 +287,18 @@ class UserBadgeSerializer(serializers.ModelSerializer):
     """用户奖章序列化器"""
 
     badge = ProblemSetBadgeSerializer()
+    # 成就页只拿到奖章本身，看不出是哪个题单发的，这里把题单带出来。
+    # 只在这个序列化器上加：题单详情页里的奖章列表本来就在题单上下文中，不需要
+    problemset = serializers.SerializerMethodField()
 
     class Meta:
         model = UserBadge
         fields = "__all__"
 
+    def get_problemset(self, obj):
+        problemset = obj.badge.problemset
+        return {"id": problemset.id, "title": problemset.title}
+
 
 class JoinProblemSetSerializer(serializers.Serializer):
     """加入题单序列化器"""

problemset/views/oj.py

@@ -283,12 +283,12 @@ class UserBadgeAPI(AsyncAPIView):
             # 获取指定用户的徽章
             try:
                 target_user = await User.objects.aget(username=username, is_disabled=False)
-                badges = UserBadge.objects.select_related("badge").filter(user=target_user).order_by("-earned_time")
+                badges = UserBadge.objects.select_related("badge__problemset").filter(user=target_user).order_by("-earned_time")
             except User.DoesNotExist:
                 return self.error("用户不存在")
         else:
             # 获取当前用户的徽章
-            badges = UserBadge.objects.select_related("badge").filter(user=request.user).order_by("-earned_time")
+            badges = UserBadge.objects.select_related("badge__problemset").filter(user=request.user).order_by("-earned_time")
 
         badge_list = [badge async for badge in badges]
         return self.success(await self.async_serialize_data(UserBadgeSerializer, badge_list, many=True))