Request with a SID as input parameter do not contain the domain name,
hence is must be tried to resolve the SID first before the corresponding
domain can be looked up.
https://fedorahosted.org/freeipa/ticket/3596
This extop can be used by clients of the IPA domain, e.g. sssd, to
retrieve data from trusted external domains. It can be used e.g. to map
Windows SIDs to user or groups names and back.