Add configurable queue overflow strategy

If a queue is to be overflowed by a delivery it can reject
the delivery or drop messages from the head.
To reject delivery overflow can be configured to `reject_publish`,
to drop head it's `drop_head` (default setting).

Messages which will be rejected should still confirm being routed,
so mandatory expectations are not accumulated on the channel side.

Slave nodes will only confirm if a message was published or discarded.
To drop confirms from slaves, all confirms for a message are cleared
when the message is rejected.

When promoting a new master, left-behind deliveries should
be rejected if the queue is full, just like normal deliveries.

Fixes #995
[#151294447]

0 files changed, 0 insertions, 0 deletions