[ASHMEET555]

Issue number: closes #8696

Summary

Changes

• In ConsumerRecordRecords.key, replace truthiness check if not key: with identity check if key is None:. This ensures Kafka events with empty string keys ("key": "") are deserialized properly rather than treated as absent and returning None.
• Align behavior with KafkaEventRecord.decoded_key in aws_lambda_powertools.utilities.data_classes.kafka_event.
• Add functional regression test test_kafka_consumer_default_deserializer_key_is_empty_string.

User experience

• Before: When a Kafka consumer record contained an empty string key ("key": ""), accessing record.key returned None, making it indistinguishable from a null/missing key.
• After: Missing or None keys return None. An empty string key is preserved and deserialized (returning "" by default, or passed to the configured deserializer).

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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[SumiRann1]

Viewed, I think this is correct!

[leandrodamascena]

Thanks @ASHMEET555, confirmed. One thing I checked before approving: with a key schema configured, an empty key now raises KafkaConsumerDeserializationError instead of silently becoming None. That is exactly what value already does for an empty value with a schema, so the two are consistent now, and I'll call it out in the release notes.

I'm approving now. This goes out in 3.40.0, so it will sit here for a while before I merge it. No rebase needed in the meantime, and you'll be credited in the release notes.