Get SMS queue statistics for monitoring.
Returns the number of active and pending messages in each provider queue.
Args: provider: Optional provider filter (twilio, vonage, telnyx)
Returns: SMSQueueStatsResponse: Queue statistics
provider (string, optional): Filter queue stats to one provider. Supported values include twilio, telnyx, and vonage.timestamp and a queues object keyed by provider.Bearer authentication header of the form Bearer <token>, where <token> is your auth token.