+                                               ->addDefaultsIfNotSet()
+                                               #XXX: ignoreExtraKeys(bool $remove = true)
+                                               ->ignoreExtraKeys(false)
+                                               ->children()
+                                                       ->scalarNode('admin')->cannotBeEmpty()->defaultValue($defaults['default']['admin'])->end()
+                                                       ->scalarNode('civility')->cannotBeEmpty()->defaultValue($defaults['default']['civility'])->end()
+                                                       #TODO: see if we can't prevent key normalisation with ->normalizeKeys(false)
+                                                       ->arrayNode('languages')
+                                                               ->treatNullLike([])
+                                                               ->defaultValue($defaults['default']['languages'])
+                                                               ->scalarPrototype()->end()
+                                                       ->end()
+                                                       #TODO: see if we can't prevent key normalisation with ->normalizeKeys(false)
+                                                       ->arrayNode('locales')
+                                                               ->treatNullLike([])
+                                                               ->defaultValue($defaults['default']['locales'])
+                                                               ->scalarPrototype()->end()
+                                                       ->end()
+                                                       ->arrayNode('group')
+                                                               ->treatNullLike([])
+                                                               ->defaultValue($defaults['default']['group'])
+                                                               ->scalarPrototype()->end()
+                                                       ->end()
+                                               ->end()