user: handle user.attributes getter for multiple attributes (#32025)

src/authentic2/custom_user/models.py

@@ -86,7 +86,11 @@ class Attributes(object):
         if self.verified and (not atv or not atv.verified):
             return None
         if atv:
-            return atv.to_python()
+            if not isinstance(atv, (list, tuple)):
+                return atv.to_python()
+            else:
+                # multiple
+                return list(map(lambda x: x.to_python(), atv))
         return None