OK… Thanks jmangelo… I’m the one that is confused and sorry I wasn’t more clear. What I thought the custom action scripts were for were to implement client side. My goal is to create users and save them to my mongo db when someone logs in through Auth0. I was under the impression I had to take the action scripts and put them into my app (whether in my backend files or client side files I did not know - noobie 
So essentially I can just turn on my custom db connection, customize the action scripts, and then my client app would auth0magically add users to my db?