Error when login with admin email

The seeds file create an admin user from the `ADMIN_EMAIL` environment variable:
https://github.com/dwyl/auth/blob/3a9d68720c02d2a8bdec33ffd8b70c35a4e5289a/priv/repo/seeds.exs#L20-L28

When login with this email using email/password the user is retreived from the database and the welcome page is displayed:
https://github.com/dwyl/auth/blob/3a9d68720c02d2a8bdec33ffd8b70c35a4e5289a/lib/auth_web/controllers/auth_controller.ex#L254-L261

However when the user was created with the seed, the value `auth_provider` is nil which then create an error on the following line:
https://github.com/dwyl/auth/blob/main/lib/auth_web/templates/auth/welcome.html.eex#L7

I think we can add the value `email` for `auth_provider` for the admin