Use key storage in object services in order to sign requests with private
session key within user session.
Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>
Add FullRange option to get range operation parameters that allows to get
payload range [0:object_size] w/o the actual knowledge of the object size.
Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>