Configure the Janus VideoRoom plugin to host a multi-party SFU session

Steps

1. Ensure the Janus gateway is compiled with the VideoRoom plugin enabled (it is included by default); edit janus.plugin.videoroom.jcfg to set global defaults such as admin_key for room management and whether rooms are recorded by default.
2. Create a room by sending a Janus API message to the videoroom plugin handle with request: 'create', including room (integer), description, bitrate, max_publishers, and optionally record: true with rec_dir pointing to your recording path.
3. Each participant establishes a Janus session via HTTP long-poll or WebSocket, attaches to the videoroom plugin, and sends a join message with request: 'join', room, ptype: 'publisher', and display name.
4. After joining as publisher, the client sends an offer SDP in a publish request; Janus responds with an answer SDP. The client then sends trickled ICE candidates via the trickle Janus API message.
5. To subscribe to another publisher, create a separate plugin handle, join with ptype: 'subscriber', and specify the publisher's feed ID; Janus sends an offer for the subscriber handle and the client answers.
6. Manage rooms server-side via the Janus Admin API (requires admin_secret) or via plugin messages with the admin_key to list rooms, kick participants, or destroy rooms.