Previously, msg.Ack(true) was used, which is mostly used for batch
processing. It mistakenly acknowledged all previously unacknowledged
messages, causing errors from the AMQP server. Now, messages are
acknowledged individually after each one is processed.
Messages that ERs failed to process are now rejected and requeued
for future processing attempts.
The reader is now closed immediately if the message delivery
channel closes. Therefore, it prevents an endless loop by avoiding
continuous consumption from empty or closed channels.
Addresses: #4146
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