[horde] First time customization of user settings

[ska]

Hello,

I've read:

http://wiki.horde.org/CustomizingPreferences
http://marc.info/?l=imp&m=114091626918979&w=4
http://marc.info/?l=horde&m=111632229923282&w=4 (this one has some entry
in the Wiki also)

My problem is that I want to have Horde authenticate via IMP against the
IMAP server - which runs well.
Then store all and any user setting within its own Horde DB, incl.
address book etc.pp. This seems to work as well, accept that I'm not
able to add GPG keys and certs to any address book members, but I'll see.

I want to pre-configure the settings of all users with basic
information, so that most of them can do their work without any
customization, that includes:

+ their name (identity etc.pp)
+ Ingo Sieve script (vacation requires personalized recipient mail
addresses)
+ address book with some standard entries with public GPG keys and certs
attached

I'm a bit lost, in which direction I shall go in order to prepare, for
instance, the Ingo Sieve script and the address book entries.
It would be nice, if this would happen at the first time a new user logs
in - this would mean to implement something like
function _prefs_hook_from_addr($user = null)
taken from the first link, because this function is called only, when
the value is not set already, and manipulate the user's data via
$users_identities = &Identity::singleton('none',"$name")
as shown in the _horde_hook_postauthenticate() snippet of David Komanek?

I suspect that I need to dig deep into the Horde API to get all, e.g.
Ingo right, needn't I?

The second link says to use the prefs.php files, but there is no such
setting for the address book or the Sieve script, right?

Finally, the third link suggests to patch the Horde DB directly. OK,
actually this would be my way to go:
1) make a DB dump,
2) setup a dummy user,
3) make another DB dump,
4) diff both dumps and replicate the entries for all users.
This way I would bypass all the Horde API, with the huge disadvantage
that a slight change in the DB possibly kills all the effort and all
users have to be prepared before they login, but with the advantage that
it looks promising quick.