> I think the correct one is
> <authorization-identifier/>. It's in XEP-0388 which is the official
> definition of the urn:xmpp:sasl:2 namespace. I confirmed it's also
> what Prosody is using, and lots of client implementations were
> developed against Prosody.
Thanks for clarification!
So <authorization-identifier/> it is.
Regards,
Andrzej