mod_rest: Roundtrip disco and items when string or boolean is used E.g. {disco:true} turns to <query/> and back to {disco:true}, same with {items:true}. Similarily, {disco:"node"}, {items:"node"} turn into <query node="node"/> and back.

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.