What is the simplest solution for organizing public WiFi, taking into account the existing ZyWall USG100+ equipment?

Question

WiFi

The entire network is working correctly. There is no point in changing equipment.
Now users have direct access to the Internet through more than 20 access points with an AP controller. All on Zyxel NWA 3160-n. The main gateway, aka DHCP for ZyWall USG100+ clients. Internet access is provided directly.
Advise how, without changing the hardware, to configure authorization in accordance with the Federal Law. Preferably by SMS.
There are a lot of servers not loaded. All on Windows Server different versions. Everything is licensed, so there is no desire to install UNIX'oid systems.
Extract from the federal law

In particular, the document provides that the telecom operator, before opening access to the Internet, can offer the user:

• enter your mobile phone number, to which a code will be sent to confirm the entered data;
  
• indicate their last name, first name and patronymic, confirming them with an identity document, an account on the Unified Portal of Public Services, or in another way that does not contradict the law.
  

It is assumed that these methods will allow you to uniquely identify the identity of the subscriber.
Recall that the identification procedure was developed in pursuance of the Federal Law of May 5, 2014 No. 97-FZ "On Amendments to the Federal Law "On Information, Information Technologies and Information Protection" and certain legislative acts of the Russian Federation on streamlining the exchange of information with use of information and telecommunication networks”, adopted as part of a package of laws that tighten measures against terrorism.
Taken from the GUARANTEE.

Answer 1

All the same, it will be cheaper to buy a Mikrotik license, install it on x86. The points can be left the same.