DGS-22899 Fix support for wrapped Avro unions

[rayokota]

What

Fix support for wrapped Avro unions. A wrapped union can either be a tuple containing the type name and value, or a dict with an extra "-type" field with the type name.

Checklist

• [Y] Contains customer facing changes? Including API/behavior changes
• [Y] Did you add sufficient unit test and/or integration test coverage for this PR?
  • If not, please explain why it is not required

References

JIRA:

Test & Review

Open questions / Follow-ups

[confluent-cla-assistant]

🎉 All Contributor License Agreements have been signed. Ready to merge.
_{Please push an empty commit if you would like to re-run the checks to verify CLA status for all contributors.}

[Copilot]

Pull Request Overview

This PR adds support for wrapped Avro unions in the schema registry serialization/deserialization logic. The changes enable proper handling of two union representation formats: tuple-based wrapped unions and dictionary-based typed unions.

• Added logic to detect and handle wrapped union types (tuples) and typed unions (dictionaries with '-type' key)
• Updated the union resolution to preserve the wrapper format during transformations
• Added comprehensive test coverage for both wrapped and typed union scenarios with field encryption

Reviewed Changes

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

File	Description
src/confluent_kafka/schema_registry/common/avro.py	Added tuple type support and modified _resolve_union to handle wrapped and typed unions, preserving tuple wrappers during transformation
tests/schema_registry/_sync/test_avro_serdes.py	Added synchronous tests for wrapped and typed union encryption scenarios
tests/schema_registry/_async/test_avro_serdes.py	Added asynchronous tests for wrapped and typed union encryption scenarios

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[sonarqube-confluent]

Quality Gate passed

Issues
2 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
96.3% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube