Azure OAuth: Github connected accounts don't fill in uid (Email)

[xtsAU]

Hi there,

I'm new on GitHub and don't actually know how to create a pull request but I found a change that fixes the issue I had with python-social-auth (in combination with the django packages) not filling in the uid field (email) when authenticating a private (individual) microsoft account that was connected to GitHub and uses the Github email.

If you do that (at least for me) a second login, or a registration from another account that uses the github email, it doesn't work since None is already used and the uid must be unique. (I use django-social-auth in combination with python-social-auth, but the fix lies in the social-core pipeline)

So i figured out the uid field would be correctly filled when changing the social-core pipeline function "social_uid" to the following:

def social_uid(backend, details, response, *args, **kwargs):
    if backend.name == 'azuread-oauth2' and details.get('email'):
        uid = details.get('email')
    else:
        uid = backend.get_user_id(details, response)
    return {'uid': uid}

Super simple, I know and something you guys probably have a deeper understanding from and can fix this at a deeper level, but that's my little contribution (if the error wasn't caused by myself somehow in the first place)

Thanks for creating and maintaining this great piece of software, though!