The Federated Credential Management API (or FedCM API) provides a standard mechanism for identity providers (IdPs) to make identity federation services available on the web in a privacy-preserving way, without the need for third-party cookies and redirects. This includes a JavaScript API that enables the use of federated authentication for activities such as signing in or signing up on a website.
Oh, I’m not calling for anyone to hold out (well, maybe except until this is widely supported across browsers), just encouraging folks to participate in the experimentation going on in that thread.