fix(authentication-azure): preserve caller-owned async credentials

[RKS (rksharma-owg)]

AzureIdentityAccessTokenProvider closes an async credential immediately after retrieving a token. Reusing that credential for a later request, sharing it across providers, or acquiring tokens concurrently can then fail because its transport is already closed.

Leave the caller-owned credential open after token acquisition, matching the synchronous path. Document that the application must close it after all clients have finished, using its async context manager or await credential.close().

Validation (Python 3.12):

• Three regressions failed on the original code: sequential requests, two providers sharing one credential, and concurrent requests. Tests use a credential double with an observable closed state and exercise the real provider; no live Azure credentials or network calls are needed.
• Authentication Azure package: pytest -q — 21 passed.
• YAPF, isort, mypy, wheel build, and git diff --check passed.
• Pylint exited successfully with 10/10; it also reports the existing unrecognized suggestion-mode configuration option.

Closes #528. Related lifetime discussion: #365.

Prepared with AI assistance; reproduction and validation ran locally.

[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

See analysis details on SonarQube Cloud

[Vincent Biret (baywet)]

Thanks for the contribution!

[Copilot]

🟢 Approval recommended

No unresolved review issues were identified, and validation covers the credential lifetime changes.

Pull request overview

Preserves caller-owned async Azure credentials for reuse and concurrent requests, while documenting caller-managed cleanup.

Changes:

• Removed implicit credential closure.
• Added regression tests for reuse, sharing, and concurrency.
• Documented credential lifetime responsibilities.

File summaries

File	Description
packages/authentication/azure/tests/test_azure_identity_access_token_provider.py	Tests credential reuse and concurrency.
packages/authentication/azure/README.md	Documents caller-managed cleanup.
packages/authentication/azure/kiota_authentication_azure/azure_identity_access_token_provider.py	Preserves credential lifetime.

Review details

• Files reviewed: 3/3 changed files
• Comments generated: 0
• Review effort level: Lite

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