✨(backend) draft initial Room viewset for external applications

From a security perspective, the list endpoint should be limited to return only
rooms created by the external application. Currently, there is a risk of
exposing public rooms through this endpoint.

I will address this in upcoming commits by updating the room model to track
the source of generation. This will also provide useful information
for analytics.

The API viewset was largely copied and adapted. The serializer was heavily
restricted to return a response more appropriate for external applications,
providing ready-to-use information for their users
(for example, a clickable link).

I plan to extend the room information further, potentially aligning it with the
Google Meet API format. This first draft serves as a solid foundation.

Although scopes for delete and update exist, these methods have not yet been
implemented in the viewset. They will be added in future commits.

env.d/development/common.dist

@@ -69,3 +69,4 @@ FRONTEND_USE_PROCONNECT_BUTTON=False
 # External Applications
 APPLICATION_JWT_AUDIENCE=http://localhost:8071/external-api/v1.0/
 APPLICATION_JWT_SECRET_KEY=devKey
+APPLICATION_BASE_URL=http://localhost:3000