flutter webview javascript channels and Stripe connect completion via cloud functions

Question

I have the following WebView Widget / I am trying to trigger the completion (or not) of a StripeConnect account creation, in order to close the View. I can t find any doc about what should be the triggered channel.

child: WebView(
          initialUrl:
              stripeConnecturl,
          javascriptMode: JavascriptMode.unrestricted,
          javascriptChannels: [
            JavascriptChannel(name: 'response', onMessageReceived: (s) {
              print('everything is okay');
              print(s.message);
              Navigator.pop(context);
            }),
          ].toSet(),

and here s my Cloud function

exports.connectStripeExpressAccount = functions.https.onRequest((req, res) =>{
  console.log('query state is  ----> ' + req.query.state);
  const authCode = req.query.code;
  return stripe.oauth.token({
    grant_type: 'authorization_code',
    code: authCode,
  }).then(async response => {
      var connected_account_id = response.stripe_user_id;
      const uid = req.query.state
      const writeResult = await admin.firestore().collection('Registration').doc(uid)
                           .set({'customer_id': connected_account_id});
      return res.send("Well done, account integration is completed. You can now close the window and go back to the app");
      });
});