Do not confirmSelect more than once per channel

[sergio91pt]

Is your feature request related to a problem? Please describe.

Reactor's RabbitMQ sendWithTypedPublishConfirms() always invokes the confirmSelect() method of the underlying channel which causes a blocking RPC call.

This is especially detrimental to performance when sending a small amount of messages per Publisher/Flux, as the channel is put into confirm mode even if it already was (when using a channel pool).

Following RabbitMQ's best practices, confirms should be enabled once per channel. In fact, there's no API to disable confirms once enabled on a channel.

Describe the solution you'd like

ChannelN should keep track if confirmSelect() was successfully enabled, and if so, future invocations of this method return a Confirm.SelectOk without making a RPC call.

I can contribute a PR if there's interest in this solution 🙂

Describe alternatives you've considered

No response

Additional context

No response

[acogoluegnes]

That's a fair improvement, feel free to submit a PR. Thanks!