how to create custom external provider authentication (sign-in with ethereum)

Hello, I'm interested in integrating Ethereum sign-in functionality into ASP.NET Identity. I'm considering creating a custom external provider to facilitate user sign-ins using signatures from their crypto wallets. Auth0 has already implemented this feature, as demonstrated [here](https://auth0.com/blog/sign-in-with-ethereum-siwe-now-available-on-auth0). Essentially, the user signs a message, and we verify the signature. Could someone please provide guidance on how to integrate this into ASP.NET Identity?