   response: {
                    clientDataJSON: base64UrlEncode(credentials.response.clientDataJSON),
                    attestationObject: base64UrlEncode(credentials.response.attestationObject)
                }
            };

            // Send credentials back to server to save
            let res = await fetch(`/register/finish?authid=${authid}`, {
                method: 'POST',
                headers: {
                    'Content-Type': 'application/json'
                },
                b