Channel for WebRTC signaling relay.

Topic: signaling:<room_id>

A room is a lobby: Gamend.Signaling derives everything from the lobby's server-owned webrtc_* columns, so this channel keeps no membership list of its own and nothing here can drift from the lobby.

Lifecycle

On join the authenticated user_id is used directly as the user identity, and Signaling.authorize/2 decides both whether the join is allowed and which role it gets — :host or :user. Clients cannot ask for a role. In a :star room the host is lobby.webrtc_host_id, or lobby.host_id when that is unset; a :mesh room has no host.

If the same user_id reconnects within the configured grace period, the existing user is preserved and a user_rejoined event is broadcast.

Messages

Inbound events (from client):

push("offer", %{target: "user-uuid", sdp: "..."})
push("answer", %{target: "user-uuid", sdp: "..."})
push("ice", %{target: "user-uuid", candidate: "..."})
push("broadcast_offer", %{sdp: "..."})   # star host only
push("list_users", %{})

Outbound events (to client):

"offer"         — %{sdp: "...", from_user_id: "..."}
"answer"        — %{sdp: "...", from_user_id: "..."}
"ice"           — %{candidate: "...", from_user_id: "..."}
"user_joined"   — %{user_id: "...", role: :host | :user}
"user_rejoined" — %{user_id: "...", role: :host | :user}
"user_left"     — %{user_id: "..."}
"room_closed"   — %{}