JWTPayload method
Implementation
String? JWTPayload(String? secret) {
var parts = this.split('.');
if(parts.length != 3)
throw 'invalid jwt token';
if(secret == null)
return jsonDecode(parts[1].FromBase64UrlToString);
if(Hmac(sha512, utf8.encode(secret)).convert(utf8.encode(parts[0]+'.'+parts[1])) == parts[2])
return jsonDecode(parts[1].FromBase64UrlToString);
else
throw 'invalid jwt sing';
}