Spectral Web Services
How to set up social sign-in on your Ghost theme
Yes, you can hire me to do this work, but if you'd like to DIY it, here's some sample code.
Social Sign-on
How to set up white-labeled Ghost sign in with your social accounts
Not really a normal blog post, but sketchy directions for Social Sign On.
Single sign-on for Ghost
Log on to Ghost using one of your "social" credentials, instead of the typical "magic link" approach.