createCodeVerifier function
Generates a random code verifier for the auth code flow.
Implementation
String createCodeVerifier() {
const length = 128;
const characterSet =
'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-._~';
var codeVerifier = '';
for (var i = 0; i < length; i++) {
codeVerifier += characterSet[_random.nextInt(characterSet.length)];
}
return codeVerifier;
}