Refactor language and role enums; update user language default value

docs/index.md

@@ -66,7 +66,7 @@ class AppEntity(BotEntity):
             back_populates="entities",
             sa_relationship_kwargs={
                 "lazy": "selectin",
-                "foreign_keys": "Entity.user_id",
+                "foreign_keys": "AppEntity.user_id",
             }
         ),
         caption="User",