fix: add DLQPolicy.DeadLetterTopicProducerName

[thomas-bousquet]

Motivation

When the retry mechanism is enabled, the RLQ producer first sends messages to the RLQ topic using the producer name if passed in the producer options inside the DLQPolicy.
However, with DLQPolicy.ProducerOptions.Name set, when the delivery count is reached and the consumer Nack() the messages, the DLQ producer sending messages to the DLQ uses RLQ producer name.

This is an issue, especially for message deduplication process where each producers must have a globally unique name for a given topic.

Modifications

This PR adds the DeadLetterTopicProducerName field to the DLQPolicy in order to either allow using a custom producer name or let the client create the producer name with the existing naming pattern.

Verifying this change

• Added integration test TestWithoutDeadLetterTopicDeadLetterTopicProducerName
• Added integration test TestWithDeadLetterTopicDeadLetterTopicProducerName

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API: no
• The schema: no
• The default values of configurations: no
• The wire protocol: no

Documentation

• Does this pull request introduce a new feature? no
• The DeadLetterTopicProducerName field added is documented where it's defined in the DLQPolicy struct

[lhotari]

LGTM

[Copilot]

Pull Request Overview

This PR fixes an issue where the DLQ (Dead Letter Queue) producer incorrectly uses the RLQ (Retry Letter Queue) producer name when sending messages to the DLQ topic. The fix adds a new DeadLetterTopicProducerName field to the DLQPolicy struct to allow specifying a custom producer name for the DLQ or letting the system generate one using the existing naming pattern.

• Adds DeadLetterTopicProducerName field to DLQPolicy struct for configuring DLQ producer names
• Updates DLQ router logic to use the new field instead of incorrectly using RLQ producer name
• Adds comprehensive integration tests to verify both custom and auto-generated DLQ producer names

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
pulsar/consumer.go	Adds the new DeadLetterTopicProducerName field to the DLQPolicy struct with documentation
pulsar/dlq_router.go	Updates producer name logic to check and use the new DeadLetterTopicProducerName field
pulsar/consumer_test.go	Adds two integration tests to verify the new functionality works correctly

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[thomas-bousquet]

Looks like CI failed with a timeout in the 1.23 run. Would it be possible to rerun it since it passed with 1.24?