Documentation on Project Scoped Users and external auth providers.

[reshmakh]

There is definitely room for improvement in the docs on the project scoped user

This page https://www.medplum.com/docs/api/fhir/medplum/projectmembership and this page https://www.medplum.com/docs/auth/user-management-guide#users should have specific references on how to check whether a user is project scoped.

It should also note the limitations of project scoped users - such as can't sign into Medplum app.
We should have explicit

People are also confused about IDPs per-client vs. per-domain.