Microsoft Graph API's User entity has field "userType". According to documentation there is no any information about this. There is one line: "A string value that can be used to classify user types in your directory, such as “Member” and “Guest”. Supports $filter.". So there is no any limitations :-)
- Can be "userType" null? I can't PATCH existing user manually via graph api - graph api return an error. But on production we have some users, which have "userType": null
- Which values are valid for "userType"? Can you provide it in documentation or here please?