Add check_group_lookup_args and service_metadata to auth providers

data/users/database.py

@@ -28,3 +28,14 @@ class DatabaseUsers(object):
     """ No need to implement, as we already query for users directly in the database. """
     return (None, '', '')
 
+  def check_group_lookup_args(self, group_lookup_args):
+    """ Never used since all groups, by definition, are in the database. """
+    return (False, 'Not supported')
+
+  def iterate_group_members(self, group_lookup_args, page_size=None, disable_pagination=False):
+    """ Never used since all groups, by definition, are in the database. """
+    return (None, 'Not supported')
+
+  def service_metadata(self):
+    """ Never used since database has no metadata """
+    return {}