Store the actual domain username in the user model

[cbaerike]

This change includes 2 things:

• in UpdateUsers(), the previous code converted UserPrincipal objects into username strings, then back into UserPrincipal objects ... losing the original UserPrincipal.Context on the way, and with that any way to determine the actual user domain.
• the UserPrincipal.UserPrincipalName property does not always contain the correct domain name after the @ character (e.g. in environments where an internal "company.local" domain was connected with Office 365, and all users received the external email address as their UPN. Using the SamAccountName and user.Context.Name instead fixes this.

[cbaerike]

Just saw issue #738 - this PR will fix it.

[gabriel-alecu]

Hello!

Any reason why this hasn't been merged yet?
I just installed Bonobo and am facing the same issue.

[willdean]

Unfortunately this is the kind of change seems almost certain to break something in the very complex matrix of different auth permutations, many of which I'm not actually able to test here.

For example, I am somewhat sceptical that user.SamAccountName + "@" + user.Context.Name is a universally better way to get the name of a principal than user.UserPrincipalName, even though I do recognise that it probably works better for some people in some situations.

Something more adaptable is probably needed here, though I'm not really sure what.