DGS-22077 Fix IndexOutOfBoundsException when evolving Avro schema w/rules

[rayokota]

What

Fix IndexOutOfBoundsException when evolving Avro schema w/rules. Add code to ensure the schema of the message is used when transforming fields of the message.

Checklist

Please answer the questions with Y, N or N/A if not applicable.

• [Y] Contains customer facing changes? Including API/behavior changes
• [N] Is this change gated behind config(s)?
  • List the config(s) needed to be set to enable this change
• [Y] Did you add sufficient unit test and/or integration test coverage for this PR?
  • If not, please explain why it is not required
• [N] Does this change require modifying existing system tests or adding new system tests?
  • If so, include tracking information for the system test changes
• [N] Must this be released together with other change(s), either in this repo or another one?
  • If so, please include the link(s) to the changes that must be released together

References

JIRA:

Test & Review

Open questions / Follow-ups

[confluent-cla-assistant]

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[Copilot]

Pull Request Overview

This PR fixes an IndexOutOfBoundsException that occurs when evolving Avro schemas with rules by ensuring the correct schema is used during message transformation.

• Updates the transformMessage method to use the schema from the message itself when available, enabling proper schema evolution
• Adds comprehensive test coverage for specific Avro serialization scenarios with field transformations and schema evolution

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
client/src/main/java/io/confluent/kafka/schemaregistry/avro/AvroSchema.java	Fix schema evolution issue by using message's schema when available during transformation
schema-rules/src/test/java/io/confluent/kafka/schemaregistry/rules/cel/CelExecutorTest.java	Add test coverage for specific Avro serialization with field transformations and missing properties

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[rayokota]

/sem-approve

[Claimundefine]

LGTM