mod_rest: Add special handling to catch MAM results from remote hosts Makes MAM queries to remote hosts works. As the comment says, MAM results from users' local archives or local MUCs are returned via origin.send() which is provided in the event and thus already worked. Results from remote hosts go via normal stanza routing and events, which need this extra handling to catch. This pattern of iq-set, message+, iq-result is generally limited to MAM. Closest similar thing might be MUC join, but to really handle that you would need the webhook callback mechanism.

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.