GetOnPremisesRequestDigestInfoAsync doesn't force windows authentication when multiple authentications are enabled

Category

• Bug

Describe the bug

From ConfigureOnPremisesContext, we use "X-FORMS_BASED_AUTH_ACCEPTED"=f header to force windows authentication, however this header is not configured when retrieve the form digest info GetOnPremisesRequestDigestInfoAsync, so the forbidden exception will be returned for the GetOnPremisesRequestDigestInfoAsync method.

Steps to reproduce

• Enable multiple authentications in SharePoint On-Premise environment
• Test the convert classic page to modern page test case (https://learn.microsoft.com/en-us/sharepoint/dev/transform/modernize-userinterface-site-pages-powershell#read-publishing-page-in-on-premises-sharepoint-and-create-the-modern-page-in-sharepoint-online)

Expected behavior

The PowerShell is able to connect the source on-premise environment when multiple authentications are enabled.

Environment details (development & target environment)

• SDK version: 1.12.2.0
• OS: Windows
• SDK used in: [PnP PowerShell]
• Framework: [.NET Core v6 ]

Additional context

Start in src/lib/PnP.Framework/Extensions/ClientContextExtensions.cs at GetOnPremisesRequestDigestInfoAsync and compare it with ConfigureOnPremisesContext in src/lib/PnP.Framework/AuthenticationManager.cs. Reproduce the multiple-authentication SharePoint on-premises scenario using the documented page-conversion test case. Done means the digest request succeeds and PnP PowerShell can connect to the source environment.