Add helper command to get a certificate's proof of possession

Is your feature request related to a problem? Please describe the problem.

I am attempting to use Add-MgApplicationKey but I cannot without generating a Proof. There does not appear to be an easy way to do this using PowerShell. The documentation https://learn.microsoft.com/en-us/graph/application-rollkey-prooftoken?tabs=csharp-1 only offers a C# example and some of the Microsoft.IdentityModel.* libraries don't appear to be present within the Microsoft Graph module or installed by default on a system.

I'm attempting to migrate away from some legacy scripts that utilize the AzureAD module and hit a road block with this one.

Describe the solution you'd like.

Being able to generate a proof with a cmdlet provided by the Microsoft Graph module in PowerShell would make using this cmdlet easier. A working example would also be sufficient.

Additional context?

This issue appeared to previously come up in #779 and #817. The outcome seems to have been a PowerShell example in the documentation, but recent versions do not contain the example, and looking at the history of the document, the old example does not function properly. Could the resolution to these be revisited?

Start with the Add-MgApplicationKey workflow and compare the linked Microsoft Graph proof-of-possession documentation with the earlier discussions in issues #779 and #817. Verify whether the historical PowerShell example still works and identify the appropriate Microsoft Graph module entry point for a helper cmdlet or example. Done means a working PowerShell path can generate the proof required by Add-MgApplicationKey.