How can I go about developing a HttpService Roblox User Verification System?

Basically, I'm starting up a website Roblox related that users can register on, and I'd like a way for them to verify their account on my site to their Roblox account. This functionality is found in sites such as ScriptingHelpers and Terabyte Services. I've looked all over online, but have found nothing on checking a specific code or string of text in a user bio... how can I go about doing this from a website?

This is only an explanation

What I did for my verification system is this, first let's start on the website, on a verifacation page we enter in our Roblox username and when we press continue it saves both the username and code that the page generates to a mysql database. next we create another page that handles requests from Roblox. on the Roblox place we make it so that as soon as you get inside the game it sends out a get request checking if you have any verifications you need to take care of (your username that you saved in mysql) if you do the place will create something where you will need to enter your code down that was generated (also saved to mysql) then it will send a post to the page that handles the Roblox requests and if the code is the same as the code saved inside mysql and its the same row with the username then it will set things up, tada. I used php for the web server side. If you have questions ask.