Write a message to a User. Contrary to pm_broadcast(), the message is archived and/or deleted on the sender side only if requested. The message may come from an untrusted application, a gateway for example, so it may be useful to involve some auto moderators in the processing.
(sender, recipient, subject, body='', skip_notification=False,
auto_archive=False, auto_delete=False, auto_moderators=None)
source not stored for this graph (policy: none)