anchor.diff:  %%--------------------------------------------------------------------
   %% @doc A privilege level of a group user.
   %%--------------------------------------------------------------------
  --spec group_user() -> privileges(group_privilege()).
  -group_user() ->
  +-spec group_member() -> privileges(group_privilege()).
  +group_member() ->
       from_list([?GROUP_VIEW]).
   
   %%--------------------------------------------------------------------
  
positive.code: %%--------------------------------------------------------------------
  %% @doc A privilege level of a handle user.
  %%--------------------------------------------------------------------
  -spec handle_user() -> privileges(handle_privilege()).
  handle_user() ->
      from_list([?HANDLE_VIEW]).
  
  %%--------------------------------------------------------------------
  
negative.code: %%--------------------------------------------------------------------
  -spec handle_admin() -> privileges(handle_privilege()).
  handle_admin() ->
      union(handle_member(), [
          ?HANDLE_UPDATE,
          ?HANDLE_DELETE
      ]).
  