Warn against DebeziumIO not resilient to worker crash or restart

[Abacn]

See #28248

ideally we should fix that.

DebeziumIO is implemented to use low-level APIs (SourceConnector/SourceTask) to interact with Debezium. It requires manual handling of offset tracking. It has an in memory offset tracking as a static final Map member (KafkaSourceConsumerFn.restrictionTrackers) that is not saved on worker restart.

Another problem is that it saves offset in restriction tracker (OffsetHolder), while the restriction itself is not serializable (Map<String, Object>) and persumably not saved to runner. The trySplit implementation is also need to be revisited.

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[gemini-code-assist]

Summary of Changes

Hello @Abacn, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a critical limitation in the DebeziumIO connector by adding a clear warning in its documentation. The change aims to inform users that the connector is currently experimental and lacks resilience to worker crashes or restarts, which can result in reprocessing all data from the source. This ensures users are aware of potential data consistency issues and the need for careful consideration when deploying DebeziumIO in production environments.

Highlights

• DebeziumIO Warning: Added a warning to the Javadoc of DebeziumIO indicating its experimental status and a known issue where it does not preserve offsets on worker crash or restart, leading to data re-retrieval from the beginning.
• Issue Reference: Included a reference to Issue Handling the restart with apache beam debezium application #28248 for users to find more detailed information about the resilience problem with DebeziumIO.

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[Abacn]

R: @shunping

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