mod_rest: Support parameters in callback URL
E.g.
rest_callback_url = "http://myapi.example:5000/api/{kind}/{type}"
which results in e.g. requests to /api/message/chat
Allows using path routing in web frameworks for dispatch instead of
having to pick apart the payload to further dispatch it.
Introduction
============
This module creates stub configuration files for newly activated hosts.
Configuration
=============
A single option exists, `persisthosts_path`, which is the path where new
stub configuration files are created. It defaults to `"conf.d"`, and is
treated as relative to the configuration directiory [^1] unless set to
an absolute path.
[^1]: usually `/etc/prosody` on \*nix systems