anchor.diff:          group_user(),
           ordsets:from_list([
               group_invite_user,
  -            group_remove_user
  +            group_remove_user,
  +            group_create_group_token,
  +            group_remove_group
           ])
       ).
   
  
positive.code:             group_leave_space,
              group_set_privileges,
              group_change_data,
              group_remove
          ])
      ).
  
  
negative.code: -type group_privilege() :: group_change_data | group_invite_user |
  group_remove_user | group_join_space | group_create_space |
  group_set_privileges | group_remove | group_leave_space |
  group_view_data | group_create_space_token |
  group_join_group | group_create_group_token | group_remove_group.
  
  %%%===================================================================
  %%% API
  