Add altSecurityIdentities attribute from MS-WSPP schema definition
Active Directory schema includes altSecurityIdentities attribute
which presents alternative security identities for a bindable object in
FreeIPA doesn't currently use this attribute. However, SSSD certmap
library may generate searches referencing the attribute if it is
specified in the certificate mapping rule. Such search might be
considered unindexed in 389-ds.
Define altSecurityIdentities attribute to allow specifying indexing
rules for it.
Reviewed-By: Florence Blanc-Renaud <firstname.lastname@example.org>