Using pfSense with ACT Fibernet [Tutorial]

I've encountered multiple posts about setting up pfSense with ACT Fibernet here on this forum and on reddit, and I just got it working so I am creating this thread hoping it might help someone.

1. First connect your WAN cable to any device that can open a web browser and go to selfcare.actcorp.in
2. Authenticate with your username (do not use the mobile number option because then the OTP parameter will vary and you'll have to reverse engineer the encryption code in the obfuscated js file) and password. These credentials are the same as the ones you use for PPPoE.
3. Before you press the submit button, open developer tools and go to the network tab and then press submit. You'll see a request to this URL selfcare.actcorp.in/v1/subscriberlogin/loginByUserId, right click on that and go to Copy > Copy as cURL. It will look something like this (with some extra unnecessary headers):
   

   curl 'https://selfcare.actcorp.in/v1/subscriberlogin/loginByUserId' \
     -H 'Content-Type: application/json' \
     -H 'Cookie: remote=<your-WAN-IP>; remote=<your-WAN-IP>' \
     -H 'Referer: https://selfcare.actcorp.in/home' \
     --data-raw '{"userId":"<your-encrypted-user-id>","userPwd":"<your-encrypted-user-password>,"networkType":"ACT","subscriberLoc":"","remoteIP":"<your-WAN-IP>","ecType":""}' \
     --compressed

4. Connect your WAN back to your pfSense machine.
5. Now open your pfSense admin portal and configure your WAN interface to use DHCP (even if you have a static public IP) and then replace <your-WAN-IP> in the curl command with the IP currently assigned to your WAN.
6. Open a shell on your pfSense machine and run the curl command, if you get a JSON response back then authentication was successful.
7. You can now configure your WAN interface to use PPPoE in your admin portal.
8. Everything should probably work now.