We don't use custom names and the only place where custom method option
is used it provides the default name and can be omitted.
Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>
Implement `AddKeys` / `RemoveKeys` methods to call `addKey` / `removeKey`
methods of NeoFS ID contract.
Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>