Merge branch 'stale-read-parent' into 'master'

Fix stale reads on Create/DestroyElementParent

Closes #845

See merge request !1481

arkindex/documents/serializers/elements.py

@@ -367,8 +367,8 @@ class ElementParentSerializer(serializers.Serializer):
             # Do not raise Error in order to create OpenAPI schema
             return
         corpora = Corpus.objects.writable(self.context['request'].user)
-        self.fields['child'].queryset = Element.objects.filter(corpus__in=corpora)
-        self.fields['parent'].queryset = Element.objects.filter(corpus__in=corpora)
+        self.fields['child'].queryset = Element.objects.using('default').filter(corpus__in=corpora)
+        self.fields['parent'].queryset = Element.objects.using('default').filter(corpus__in=corpora)
 
     def validate(self, data):
         errors = defaultdict(list)