Botkit: [Facebook Adapter] Error in Url Verification for BotFramework bots

[ceciliaavila]

Describe the bug

BotFramework TestBot with Facebook Adapter is not validating the Callback Url. We are experiencing an [ERR_INVALID_ARG_TYPE] exception.

_Note: Same that #1817 automatically closed due to lack of activity._

To Reproduce

Steps to reproduce the behavior:

1. Go to packages -> TestBot.
2. In botframework.js uncomment the lines to connect the bot with Facebook and provide a verify_token, an app_secret, and an access_token.
   
3. Add a get method to handle the request for URL validation:
   
4. Install and build the project. Run the bot.
5. In a Facebook Developer Account create a new app and add a Messenger product.
   
6. Expose the bot's endpoint using ngrok
7. Go back to the Facebook App and in the Webhook Section of the Messenger Product, click on _Subscribe to Events_ button
   
8. Complete the Callback URL with the ngrok URL adding '_/api/messages_', fill in the Verify Token and click _Verify and Save_ button.
   

Expected behavior

The URL should get verified.

Proposed Solution

In facebook_adapter.ts, in processActivity method, add the following code:

        var url = req.url;
        var params = url.split('?');
        var urlParams =  new URLSearchParams(params[1]);

        if (urlParams.get('hub.mode') === 'subscribe') {
            var verify_token = urlParams.get('hub.verify_token');
            if (verify_token === this.options.verify_token) {
                var challenge = urlParams.get('hub.challenge');
                res.status = 200;
                res.sendRaw(challenge);      
            } else {
                res.status = 401;
                throw new Error('Webhook not validated');      
            }
        } else {    
            if (await this.verifySignature(req, res) === true) {
                         ...

[bug]

[omkar-joshi]

I'd like to help with this

[benbrown]

This has been added to the sample code in the README, but I do not plan on adding it directly to the adapter.