Add distinct on id and created

  - TODO: determine the correct set of logic/subselects/custom sql to
  avoid using `distinct`

[#OSF-9058]

Author: mfraezz

api/base/filters.py

@@ -511,4 +511,4 @@ def preprints_queryset(self, base_queryset, auth_user, allow_contribs=True):
         else:
             query = no_user_query
 
-        return base_queryset.annotate(default=Exists(sub_qs)).filter(Q(default=True) & query)
+        return base_queryset.annotate(default=Exists(sub_qs)).filter(Q(default=True) & query).distinct('id', 'created')