The process of using your domain to log in to sites and services is called web sign-in and is implemented via a protocol called IndieAuth, an extension of OAuth used for decentralized authentication.
It's entire reason for being is to answer the simple question: does the person behind the browser have control over the URL that they are claiming as their own?
…being a completely decentralized protocol, it's much more in keeping with the spirit of the IndieWeb.
If your goal is to make a social network out of the world wide web, there is a certain elegance to the idea of leveraging DNS as a user registration system.
1.1. In my garden
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