Introduce a new viewset that lets the roomkit start a room even when
no WebRTC participant has joined yet.
This is a first entry point that will be extended over time with
more actions a roomkit needs to be able to trigger.
Known limitations:
* The responsibility around SIP rules is currently split between
the telephony feature and the roomkit one. This may need a
refactor later on to consolidate ownership in a single place.
* The default throttle might be too low for production usage and
will likely need to be revisited.
lebaudantoine