fun isConferenceStillPending(invitationId: String, onCompletion: (Either<Boolean, ConferenceError>) -> Unit): Unit
Checks if a conference associated with a specific invitationId is still pending.
invitationId - Identifier of the invitation associated with the conference.
onCompletion - Callback that will be invoked when the request is completed.
It will receive whether the conference is still pending (true) or not (false) in case of success.
In case of error, it will receive a ConferenceError.