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.
Because during startup, if all items are provided by a different module
(e.g. mod_turn_external) then this would log a scary warning even if
everything is fine after that other module has been loaded.
This way, any persistent problematic state is reported in the console.
Errors with individual items should still be reported by prepare().
Now, if you load mod_external_services alone without configuring any
services, no error or warning is reported in the log, but maybe that's
not so bad with it reported in the console.
This ensures that problems with entries added other modules, e.g.
mod_turn_external, are reported on startup. However, this depends on
load order and whether a `module:depends()` call comes before the
`module:add_item()` call. A followup commit will do something about
that.
While writing developer documentation it became obvious that i was silly
to have one item format for config and items API, and another format for
the event API.
Then there's the stanza format, but that's a common pattern.
This change reduces the possible input formats to two and allows other
modules the benefit of the processing and validation performed on items
from the config.
Kim Alvefur