Publish unacked messages to Dead Letter Exchange

[chanikag]

Description

We have been checking the documentation at[1] and it seems we have missed to add the parameter for the error exchange name.
dlq.exchange[2]
Dead letter exchange is not working and it seems it is, as you can check at this class[3] we need this value to enter to the requested flow.
Could you please check that and change the doc?

[1] https://apim.docs.wso2.com/en/4.1.0/integrate/examples/rabbitmq_examples/move-msgs-to-dlq-rabbitmq/#synapse-configurations

[2] https://medium.com/@philippbruegger/rabbitmq-requeue-delay-solution-with-wso2-b3e78af050ea

[3] https://github.com/wso2/wso2-axis2-transports/blob/v2.0.0-wso2v67/modules/rabbitmq/src/main/java/org/apache/axis2/transport/rabbitmq/ServiceTaskManager.java

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[GDLMadushanka]

Couldn't get this working with even after adding the following parameters (Rabbitmq version 4.0.3)

<parameter name="rabbitmq.message.error.exchange.name">orders-error-exchange</parameter>
<parameter name="rabbitmq.message.max.dead.lettered.count">5</parameter>

[GDLMadushanka]

need to revisit this doc issue after fixing the product issue wso2/product-micro-integrator#3777