If you attempt to make a final deployment to Heroku and get the yes / no tracking in Heroku working, there are a few things to remember:

1. In your surveyRoutes, make sure you have the correct Path Parser import:
   const { Path } = require('path-parser');

2. In the Heroku Dashboard, make sure the REDIRECT_DOMAIN variable is set to your current Heroku app URL without a trailing slash.
   ex: https://cryptic-lake-82120.herokuapp.com

3. Remember to update your Sendgrid's event webhook URL to your current Heroku app URL.
   ex: https://cryptic-lake-82120.herokuapp.com/api/surveys/webhooks

Lastly, please remember, Ngrok is not used in production in any way. This was only to allow Sendgrid to communicate the click tracking back to our server running on localhost in development. No such mechanism is required in production.