If users, projects or groups are provided by name, there is a
possibility of the existence other users/projects/groups with the same
name in other domain. Even though this is not a problem if the actual
ID is given instead of a name; this is mostly a usability enhancement.
So, three options were added, one for specifying the domain where the
user belongs, another one to specify the project's domain, and finally
one to specify the group's domain.
Change-Id: Iab04b0e04fa75ea5aa3723b8ea42a45f58a6cdb2
Closes-Bug: #1421328
3ca96ef93c