Call State 与 RealtimePhase

stateDiagram-v2
[*] --> Idle
Idle --> Incoming
Idle --> Outgoing
Incoming --> Active: accept + ready
Outgoing --> Active: ready
Incoming --> Ended: reject
Active --> Ended: hangup/close
Incoming --> Failed
Outgoing --> Failed
Active --> Failed
Ended --> Idle
Failed --> Idle