External authentication providers
Now that we finally have a fully-featured, JWT-based internal authentication provider, we can start thinking about supporting other login alternatives. Hooking up some external authentication providers such as Google, Facebook, and Twitter will undoubtedly please our users and increase our application's overall appeal.
Luckily enough, AspNetCore.Identity comes bundled with a built-in set of middleware classes for the most used OAuth2 providers that will simplify each of these tasks.
OAuth2 authorization flow
Before we start, let's do a quick recap of how the OAuth2 authorization flow actually works:
This, in short, ...