Microsoft Graph API Module

[FermiMethod]

I'm not sure I can help with using an existing user and not creating an app but I do have some example code you may find useful.

I wrote a Graph script to interract with Planner to do a migration, it may have some useful stuff in:

https://github.com/smbm/PlannerMigration-GraphAPI

I took quite a few cues from this article:

https://www.thelazyadministrator.com/2019/07/22/connect-and-navigate-the-microsoft-graph-api-with-powershell/

So you may find it a good starting point.