Extend docs with supported status returns. Add several helper functions
which allow to check the particular status.
Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>
We should provide the ability to customize private of object HEAD /
DELETE ops.
Implement `UseKey` method on `PrmObjectHead` / `PrmObjectDelete` types.
Sign requests with the specified key if called.
Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>
