JWTToken method
Implementation
String JWTToken(String secret) {
var toSing = 'eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzUxMiJ9.' + base64Url.encode(utf8.encode(jsonEncode(this)));
return toSing + '.' + base64Url.encode(Hmac(sha512, utf8.encode(secret)).convert(utf8.encode(toSing)).bytes);
}