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.
Contributing
============
Guidelines for developers
-------------------------
- Each module should be contained in a folder of its name (e.g.\
`mod_ping/mod_ping.lua`)
- Each module should have a `README.markdown` page in their folder
with a description, usage, configuration and todo sections (feel
free to copy an existing one as a template)
- Commit messages should begin with the name of the plugin they are
for (e.g. `mod_ping: Set correct namespace on pongs`)
Instructions on cloning the repository are at
<https://prosody.im/doc/installing_modules#prosody-modules>