[Feature Request] Add a .WithUser() modifier to the Microsoft Graph queries (like WithAppOnly())

[jmprieur]

Is your feature request related to a problem? Please describe.
In some scenarios not supported by Microsoft.Identity.Web , where user token validation is done by other means than AddMicrosoftIdentityWebApi, when the code processing the request wants to call Microsoft Graph on behalf of the user, it's useful to pass-in the user

Describe the solution you'd like
ClaimsPrincipal user = ...

await _graphServiceClient.Me.GetAsync(r =>
 {
     r.Options.WithUser(user)
 });