Fix google OpenID Connect

[mvschaik]

This PR fixes logins with Google OpenID Connect. It merges #687 and #693.

[nickcatal]

This should be closer to

        values = {'username': '', 'email': '', 'fullname': '',
                  'first_name': '', 'last_name': ''}

        fullname = values.get('name') or ''
        first_name = values.get('given_name') or ''
        last_name = values.get('family_name') or ''
        email = values.get('email') or ''

        if not fullname and first_name and last_name:
            fullname = first_name + ' ' + last_name
        elif fullname:
            try:
                first_name, last_name = fullname.rsplit(' ', 1)
            except ValueError:
                last_name = fullname

        username_key = self.setting('USERNAME_KEY') or self.USERNAME_KEY
        values.update({'fullname': fullname, 'first_name': first_name,
                       'last_name': last_name,
                       'username': values.get(username_key) or
                                   (first_name.title() + last_name.title()),
                       'email': email})
        return values

[mvschaik]

I appreciate your suggestion, but these fields have been standardized for OIDC in http://openid.net/specs/openid-connect-core-1_0.html#rfc.section.5.1. I therefore would prefer to use these as a sensible default. I guess most users would override the OpenIdConnectAuth to customize this for the actual values the backend provides (if the backend doesn't adhere to the RFC).

[nickcatal]

I was mostly talking about username_key = self.setting('USERNAME_KEY') or self.USERNAME_KEY

Which lets users override the username in their own settings file and exists in other backends.

[mvschaik]

I've added the USERNAME_KEY setting.

[nickcatal]

Left a few comments that I could see on first glance.

This is what I need to start to flesh out part 2 of #750 so hopefully it gets merged in.

[mvschaik]

Thanks for your suggestions, @nickcatal! I've added some fixes. I hope it gets merged in too!

[gabejackson]

Any reason this hasn't been merged yet? Have been working on something similar lately and could lend a hand getting this merged if needed.

[omab]

I've ported this PR into social-core.

Thanks!