fix: improve case-insensitive handling of Kafka headers

[psmagin]

Closes: MODLD-1117

Purpose

improve case-insensitive handling of Kafka headers

Changes Checklist

• API Changes: Document any API paths, methods, request or response bodies changed, added, or removed.
• Database Schema Changes: Indicate any database schema changes and their impact. Confirm that migration scripts were created.
• Interface Version Changes: Indicate any changes to interface versions.
• Interface Dependencies: Document added or removed dependencies.
• Permissions: Document any changes to permissions.
• Logging: Confirm that logging is appropriately handled.
• Unit Testing: Confirm that changed classes were covered by unit tests.
• Integration Testing: Confirm that changed logic was covered by integration tests.
• Manual Testing: Confirm that changes were tested on local or dev environment.
• NEWS: Confirm that the NEWS file is updated with relevant information about the changes made in this pull request.

Related Issues

https://folio-org.atlassian.net/browse/MODLD-1117

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud