Implement pagination achievements

lego/apps/achievements/pagination.py

@@ -0,0 +1,7 @@
+from lego.utils.pagination import CursorPagination
+
+
+class AchievementLeaderboardPagination(CursorPagination):
+    page_size = 25
+    max_page_size = 25
+    ordering = "-achievements_score"

lego/apps/achievements/views.py

@@ -1,22 +1,28 @@
 from rest_framework import mixins, permissions, viewsets
 from rest_framework.response import Response
 
+from lego.apps.achievements.pagination import AchievementLeaderboardPagination
 from lego.apps.users.models import User
 from lego.apps.users.serializers.users import PublicUserWithGroupsSerializer
 
 
 class LeaderBoardViewSet(mixins.ListModelMixin, viewsets.GenericViewSet):
     serializer_class = PublicUserWithGroupsSerializer
     permission_classes = [permissions.IsAuthenticated]
+    pagination_class = AchievementLeaderboardPagination
 
     def get_queryset(self):
         return (
             User.objects.filter(achievements__isnull=False)
             .order_by("-achievements_score")
-            .distinct()[:50]
+            .distinct()
         )
 
     def list(self, request, *args, **kwargs):
         queryset = self.get_queryset()
+        page = self.paginate_queryset(queryset)
+        if page is not None:
+            serializer = self.get_serializer(page, many=True)
+            return self.get_paginated_response(serializer.data)
         serializer = self.get_serializer(queryset, many=True)
-        return Response(serializer.data)
+        return Response(serializer.data)