We know, that we can't add more than one authentication for one project. I don’t know why Microsoft make this policy. Maybe it’s for business J. I think it will very good if we can set more than one authentication for more login.
I have googling to find solution how to make multiple login with one authentication in one project, and I found an url that I forgot. But I had to download an example to implement it.
I have to apply it in my latest project. And It's work.
You can find the download attachment by clicking the title of this article.