Creates new session and stores its reference if it does not exist or returns an error otherwise.
The sip address to use.
The display name to use.
Handles presence nodes with name: jibri-sip-call-state.
the presence node Object to handle. Object representing part of the presence received over xmpp.
Listener for session state changed. When a session goes to off or failed we delete its reference.
{ address, oldState, newState, displayName }
Main video SIP GW handler. Stores references of all created sessions.