Hang up a call

After a call has been established, a participant can hang up with the saved OIMSignalingInfo:

[[OIMManager manager] signalingHungUp:signalingInfo
                            onSuccess:^{ [self releaseCallResources]; }
                            onFailure:^(NSInteger code, NSString * _Nullable message) {
    [self showCallError:code message:message ?: @"Failed to hang up the call"];
}];

The success callback only means that the hang-up signaling request completed. The app must also stop capture, disconnect from the media room, and release the camera, microphone, and AVAudioSession. Make cleanup idempotent by roomID.