How to make web authorization via sms on several APs in different places?

Question

SMS

There are 13 catering establishments in different cities. Everywhere there is wifi, unifi equipment. Gave the task for all interested visitors to make authorization (in connection with the legislation). The visitor connects to wifi, an authorization window appears where he indicates his phone number to which an access code is sent to him via sms. After entering the user gets free access to the network.
What are the solutions? What tools to use? Interested in a low-budget solution. Thanks friends.

Answer 1

I myself am breaking my brain over this, but it seems that only by installing a billing system can this be realized.
And yes, regarding the law there, also pay attention to this "According to the requirement of Federal Law-436, administrators of public Internet access points are required to use filtering tools that protect children from visiting dangerous and dubious resources."
But this is easier to solve than screwing up authorization, and yes, according to authorization, then it is necessary to store information about users for 60 days .....