mod_rest: Reject password that fails saslprep earlier (thanks tgy)
Prevents an error later if/when passing the password through saslprep a
second time in the authentication module, since the prep functions now
reject nil
The error reporting could be improved but that would involve adding a
way to pass errors back out of the check_credentials() function.
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summary: Remote Roster Management
...
Introduction
============
This module adds support for [XEP-0321: Remote Roster Management] which
is commonly used to allow components such as transports to modify the
rosters of local users.