wip: single active consumer offset tracking

[l4mby]

This pr adds a consumer update listener in the consumer. In this way, the end user can customize the behaviour of a single active consumer when it becomes active. An example is also added to show how a single active consumer can resume the consuming of messages from a specific offset, upon activation.

[Copilot]

Pull Request Overview

This PR adds support for single active consumer offset tracking by incorporating a consumer update listener in the consumer, client, and connection modules, and by updating end-to-end tests to cover the new behavior.

• Introduces a consumerUpdateListener and singleActive flag in StreamConsumer.
• Updates the client logic to handle consumer update queries and offset resumption.
• Adds an end-to-end test that verifies the offset tracking mechanism when switching the active consumer.

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
test/e2e/declare_consumer.test.ts	Added a new test case for validating offset tracking with two single active consumers.
src/consumer.ts	Integrated consumerUpdateListener and singleActive flag into consumer initialization.
src/connection.ts	Introduced a debug console.log in storeOffset (likely for debugging purposes).
src/client.ts	Updated consumer declaration and added getConsumerOrServerSavedOffset logic with debug logs.

Comments suppressed due to low confidence (1)

test/e2e/declare_consumer.test.ts:220

• Remove or replace 'it.only' to ensure that the full test suite runs during CI, unless this is an intentional temporary measure.

it.only(

[Copilot]

Pull Request Overview

This PR implements a consumer update listener for single active consumers so that upon activation the consumer can resume message consumption from a previously saved offset. Key changes include:

• Adding a new consumer update listener callback in both the test and production code.
• Updating the consumer and client code to support offset updates and single active consumer behavior.
• Providing an example demonstrating how to resume consumption from a designated offset.

Reviewed Changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 1 comment.

File	Description
test/e2e/declare_consumer.test.ts	Added a new end-to-end test case for single active consumer offset tracking.
src/consumer.ts	Introduced ConsumerUpdateListener type and implementation for updating offset.
src/client.ts	Added logic to call consumerUpdateListener and update consumer offset accordingly.
example/src/single_active_consumer_update_example.js	Provided a usage example for the new consumer update behavior.

Files not reviewed (1)

• example/package-lock.json: Language not supported

Comments suppressed due to low confidence (1)

test/e2e/declare_consumer.test.ts:246

• [nitpick] Using fixed wait times in tests may lead to flaky test behavior; consider replacing fixed delays with more deterministic synchronization mechanisms (such as polling or event-based triggers) to ensure consumer state readiness.

await wait(500)