Unable configure a domin for the os_privileged_user

[Attila Fazekas]

There is no os_privileged_user_domain_name (or os_privileged_user_doamin_id) option.

Because the keystone libraries and the required parameters are frequently changing, it is advised to have dedicated section for the [privileged_user] which has the same options as the [keystone_authtoken] section.

For example manila has a [neutron], [nova], [cinder] section:
https://docs.openstack.org/ocata/config-reference/shared-file-systems/samples/manila.conf.html

IMHO cinder's privileged_user should be handled in a similar way.