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.

This module writes out a traceback to `traceback.txt` in Prosodys data
directory (see `prosodyctl about`) when the signal `SIGUSR1` is
received. This is useful when debugging seemingly frozen instances in
case it is stuck in Lua code.