Read Your Website Is Your Passport by Desmond Rivet (Desmond Rivet)

One of the themes that crops up again and again in the IndieWeb community is that your personal domain, with its attendant website, should form the nexus of your online existence. Of course, people can and do maintain separate profiles on a variety of social media platforms, but these should be subordinate to the identity represented by your personal website, which remains everyone's one-stop-shop for all things you and the central hub out of which your other identities radiate.
Part of what this means in practice is that your domain should function as a kind of universal online passport, allowing you to sign in to various services and applications simply by entering your personal URL.

A nice little primer on authorization and authentication.