feat: add Azure IMDS authentication support

[Emanuele Sabellico (emasab)]

• Updated CHANGELOG.md for v1.6.0 release with enhancements.
• Changed librdkafka version to dev_oauthbearer_metadata_based (to be changed later)
• Implemented Azure IMDS OAuth client and token provider.
• Added support for Azure IMDS in RestService.
• Refactor RestService bearer authentication methods.
• Added tests for Azure IMDS OAuth client functionality.

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What

Checklist

• Contains customer facing changes? Including API/behavior changes
• 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

Unit tests are present. Will attach test results on an Azure instance.

Open questions / Follow-ups

[Copilot]

Pull Request Overview

This PR adds Azure IMDS (Instance Metadata Service) OAuth authentication support to the TypeScript Schema Registry client, enabling authentication using Azure managed identities.

• Implements Azure IMDS OAuth client with token fetching and expiration handling
• Refactors OAuth authentication architecture with abstract base classes and builder pattern
• Adds comprehensive test coverage for Azure IMDS functionality

Reviewed Changes

Copilot reviewed 14 out of 16 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
schemaregistry/oauth/oauth-client-azure-imds.ts	New Azure IMDS OAuth client implementation with token management
schemaregistry/oauth/abstract-oauth-client.ts	New abstract base classes for OAuth clients and token providers
schemaregistry/oauth/bearer-token-provider.ts	New interface definitions for bearer token providers
schemaregistry/oauth/static-token-provider.ts	New static token provider implementation
schemaregistry/oauth/oauth-client.ts	Refactored existing OAuth client to use new abstract architecture
schemaregistry/rest-service.ts	Updated to use new bearer token provider architecture
schemaregistry/test/oauth-client-azure-imds.spec.ts	Comprehensive test suite for Azure IMDS OAuth functionality
schemaregistry/test/oauth-client.spec.ts	Updated tests to work with refactored OAuth client
schemaregistry-examples/src/kafka-oauth.ts	Added example demonstrating Azure IMDS usage
schemaregistry-examples/src/constants.ts	Added Azure IMDS configuration constant
package.json	Updated librdkafka version to development branch
lib/error.js	Updated version comment to match new librdkafka version
deps/librdkafka	Updated submodule to development branch
CHANGELOG.md	Added v1.6.0 release notes

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[Copilot]

The changelog references librdkafka v2.12.0 but the package.json uses "dev_oauthbearer_metadata_based". These versions should be consistent.

Suggested change

	1. References librdkafka v2.12.0. Refer to the [librdkafka v2.12.0 release notes](https://github.com/confluentinc/librdkafka/releases/tag/v2.12.0) for more information.
	1. References librdkafka "dev_oauthbearer_metadata_based". Refer to the [librdkafka dev_oauthbearer_metadata_based branch](https://github.com/confluentinc/librdkafka/tree/dev_oauthbearer_metadata_based) for more information.

[Copilot]

Missing semicolon after the bearerAuthCredentials object declaration.

Suggested change

	}
	};