UserItem class auth_setting needs updating

[ma7tcsp]

In TSC this parameter only accepts "ServerDefault" or "SAML".

However, in Tableau Cloud where MFA has been turned on (ie it now HAS to be turned on) this is not enough.

TSC ServerDefault maps to REST API TableauID => TableauID is no longer a valid auth REST API provides TableauIDWithMFA, and also OpenID.

OpenID is actually in the user_item.py model, however not updated in the documentation.

We need a way to set this additional REST API auth-setting values as TSC auth_setting values too. Otherwise we can't use TSC to add users to Tableau Cloud anymore.