Resolve issue where user authenticates but does not have permission to run application displaying unfriendly error

[smitthhyy]

Fixes: Issue # 20: Unfriendly text when authenticate success, but not have permission to run app.

[danieltjewett]

Hi @smitthhyy , thanks for contributing!

My initial thought was this should go into the fail method, to prevent the azurecallback method from being cluttered with potentially many conditions from Microsoft's servers. I recognize this is a condition we haven't thought through yet though and have a couple of questions.

Could we get the error_description, or something simliar, in our validating token response, a few lines down? Or does this check / response from Microsoft only happen after the user authenticates in AD? If we can get the error_description, or something simliar, later, I'd recommend moving this code in the fail method. If not, I understand the check, and would probably want to add another function to keep the azurecallback method clean of numerous conditions.

[danieltjewett]

I like where this is going. I think we need to refactor the fail method to handle better error messaging, but I don't think this PR needs to worry about that. Thanks for contributing!