GH-39345: [C++][FS][Azure] Add support for environment credential

[Tom-Newton]

Rationale for this change

Maybe be useful to support explicit environment credential (currently environment credential can be used as part of the Azure default credential flow).

What changes are included in this PR?

Are these changes tested?

There are new unittests but no integration tests that we can actually authenticate successfully. We are relying on the Azure C++ SDK to abstracting that away.

Are there any user-facing changes?

Yes, environment credential is now available.

• GitHub Issue: [C++][FS][Azure] Environment credential authentication #39345

[github-actions]

⚠️ GitHub issue #39345 has been automatically assigned in GitHub to PR creator.

[kou]

+1

Could you also update docstring?

arrow/cpp/src/arrow/filesystem/azurefs.h

Lines 162 to 167 in dcdf4e6

	/// * credential_kind: One of "default", "anonymous",
	/// "workload_identity". If "default" is specified, it's just
	/// ignored. If "anonymous" is specified,
	/// AzureOptions::ConfigureAnonymousCredential() is called. If
	/// "workload_identity" is specified,
	/// AzureOptions::ConfigureWorkloadIdentityCredential() is called.

[felipecrv]

I thought that "default" would cause the Azure SDK to automatically try to get auth parameters from the environment.

[Tom-Newton]

I thought that "default" would cause the Azure SDK to automatically try to get auth parameters from the environment.

It does but only if none of the other Auth options earlier in the chain are successful. Sometimes it's useful to be specific. E.g. if the system has multiple auths configured or if you want to quickly return an error instead of going through trying all the auths.

[conbench-apache-arrow]

After merging your PR, Conbench analyzed the 6 benchmarking runs that have been run so far on merge-commit 02585cd.

There were no benchmark performance regressions. 🎉

The full Conbench report has more details. It also includes information about 71 possible false positives for unstable benchmarks that are known to sometimes produce them.