The name of the identity for which a credential should be
acquired. It is up to the GSS-API implementation to check
whether the running process has sufficient privileges to act
on behalf of this identity.
This can be either a GSSAPI.Name object or a string. In the
latter case, the string is converted to a GSS-API name
according to a mechanism-specific default printable syntax,
i.e. just like if it would be given as the sole argument to
GSSAPI.Name.create .
If this is zero then a credential for the default principal
(if any) are retrieved.