✨(backend) add roomkit viewset to start a room without WebRTC join

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.

src/backend/core/urls.py

@@ -9,6 +9,7 @@ from rest_framework.routers import DefaultRouter, SimpleRouter
 from core.addons import viewsets as addons_viewsets
 from core.api import get_frontend_configuration, viewsets
 from core.external_api import viewsets as external_viewsets
+from core.roomkit import viewsets as roomkit_viewsets
 
 # - Main endpoints
 router = DefaultRouter()
@@ -19,6 +20,11 @@ router.register("files", viewsets.FileViewSet, basename="files")
 router.register(
     "resource-accesses", viewsets.ResourceAccessViewSet, basename="resource_accesses"
 )
+router.register(
+    "roomkit",
+    roomkit_viewsets.RoomKitViewSet,
+    basename="roomkit",
+)
 router.register(
     "addons/sessions",
     addons_viewsets.SessionViewSet,