where to register IUserTwoFactorTokenProvider type custom token provider?

[relatedrhymes]

I have created a custom google authenticator token provider implementing IUserTwoFactorTokenProvider. but I'm not sure where and how do I register this new provider in Startup?

public class GoogleAuthenticatorTokenProvider : IUserTwoFactorTokenProvider<User>
    {
        public GoogleAuthenticatorTokenProvider()
        {
        }

        public Task<bool> CanGenerateTwoFactorTokenAsync(UserManager<User> manager, User user)
        {
            return Task.FromResult(user.IsGoogleAuthenticatorEnabled);
        }

        public Task<string> GenerateAsync(string purpose, UserManager<User> manager, User user)
        {
            return Task.FromResult((string)null);
        }

        public Task<bool> ValidateAsync(string purpose, string token, UserManager<User> manager, User user)
        {
            long timeStepMatched = 0;

            var otp = new Totp(WebEncoders.Base64UrlDecode(user.GoogleAuthenticatorSecretKey));
            bool valid = otp.VerifyTotp(token, out timeStepMatched, new VerificationWindow(2, 2));

            return Task.FromResult(valid);
        }
    }