Filter by stoken: fix the done implementation for more functions

The done implementation wasn't great because it would indicate we are
not done even when we are when the last chunk returned is exactly the
size of limit.

django_etebase/views.py

@@ -288,13 +288,16 @@ class CollectionItemViewSet(BaseViewSet):
             iterator = get_object_or_404(queryset, uid=iterator)
             queryset = queryset.filter(id__lt=iterator.id)
 
-        queryset = queryset[:limit]
-        serializer = CollectionItemRevisionSerializer(queryset, context=self.get_serializer_context(), many=True)
+        result = list(queryset[:limit + 1])
+        if len(result) < limit + 1:
+            done = True
+        else:
+            done = False
+            result = result[:-1]
 
-        # This is not the most efficient way of implementing this, but it's good enough
-        done = len(queryset) < limit
+        serializer = CollectionItemRevisionSerializer(result, context=self.get_serializer_context(), many=True)
 
-        last_item = len(queryset) > 0 and serializer.data[-1]
+        last_item = len(result) > 0 and serializer.data[-1]
 
         ret = {
             'data': serializer.data,
@@ -510,13 +513,16 @@ class InvitationBaseViewSet(BaseViewSet):
             iterator = get_object_or_404(queryset, uid=iterator)
             queryset = queryset.filter(id__gt=iterator.id)
 
-        queryset = queryset[:limit]
-        serializer = self.get_serializer(queryset, many=True)
+        result = list(queryset[:limit + 1])
+        if len(result) < limit + 1:
+            done = True
+        else:
+            done = False
+            result = result[:-1]
 
-        # This is not the most efficient way of implementing this, but it's good enough
-        done = len(queryset) < limit
+        serializer = self.get_serializer(result, many=True)
 
-        last_item = len(queryset) > 0 and serializer.data[-1]
+        last_item = len(result) > 0 and serializer.data[-1]
 
         ret = {
             'data': serializer.data,