getAuthorizationPageUrl method
Returns an authorization URL to be used in a web for to allow the user to authorize the application.
Implementation
String getAuthorizationPageUrl({
    required List<Scope> scopes, required String redirectUrl, required String state}) {
  Uri authUri = Uri.parse(authorizationEndpoint);
  authUri = _appendQueryParamsToUri(authUri,
      {
        "client_id": clientId,
        "redirect_uri": redirectUrl,
        "response_type": "code",
        "state": state,
        "scope": scopes.map((e) => e.scope).join(" ")
      });
  return authUri.toString();
}