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.

This module adds a command to `prosodyctl` for listing users.

``` sh
prosodyctl mod_listusers
```