createJWT function
Implementation
String createJWT(Map<String, dynamic> payload, String secret) {
final header = {
'alg': 'HS256',
'typ': 'JWT',
};
final base64UrlHeader = base64UrlEncode(json.encode(header));
final base64UrlPayload = base64UrlEncode(json.encode(payload));
final data = '$base64UrlHeader.$base64UrlPayload';
final hmac = Hmac(sha256, utf8.encode(secret));
final signature = hmac.convert(utf8.encode(data)).bytes;
final base64UrlSignature = base64UrlEncodeBytes(signature);
return base64UrlSignature;
}