Failover with client ack mode consumer can loose a message auto acked as a duplicate

with a client ack consumer and failover after receipt but before message.ack can result in a missed message when the message is redispatched and auto acked as a duplicate.
Failover interrupt should clear dispatched and unconsumed messages so that they can get redelivered.
auto-acking a duplicate seems over eager. think best to poison pill and now that we can include a cause property it will be possible to differentiate.