mod_external_services: Factor out public function for converting to XML Along with the previous commit, allows building the XML thing yourself, should you wish to send it yourself or use it in a different context than an iq reply. API change: The 'reply' is removed from the event.

This module produces more detailed HTTP logs for Prosodys built-in HTTP
server. The format is similar to that of Apache and go into Prosodys
normal logs at the `info` level.