third_party/heimdal kdc: introduce HDB_F_USER2USER_PRINCIPAL (import lorikeet-heimdal...

third_party/heimdal kdc: introduce HDB_F_USER2USER_PRINCIPAL (import lorikeet-heimdal-202310152331 (commit a571340c9e1b75d4f5d96f08fcf9fd660d3ba3d4))

This allows HDB backends to do special handling for
User2User TGS-REQs. The main reason is to let
the HDB_F_GET_SERVER lookup to succeed even for
non-computer accounts. In Samba these are typically
not returned in HDB_F_GET_SERVER in order to avoid
generating tickets with the user password.

But for User2User the account password is not used,
so it is safe to return the server entry.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15492

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
[abartlet@samba.org Adapted to be an import from lorikeet-heimdal as requested]