[Bug] ConfidentialClientApplicationBuilder should use string.IsNullOrWhiteSpace for AzureRegion validation

[ksaaf]

Library version used

Latest

.NET version

NET 8

Scenario

ConfidentialClient - service to service (AcquireTokenForClient)

Is this a new or an existing app?

The app is in production, and I have upgraded to a new version of MSAL

Issue description and reproduction steps

This issue is identified during review of the PR 5182.

Code references to fix (there may be others).

• here
• In the validate function.

Relevant code snippets

Expected behavior

Whitspace should cause a failure.

Identity provider

Microsoft Entra ID (Work and School accounts and Personal Microsoft accounts)

Regression

No response

Solution and workarounds

No response

[bgavrilMS]

Won't fix.