I feel like a salesman because I always am bringing up azure but... You might take a look at the azure active directory b2c service. You can use stand alone azu

I feel like a salesman because I always am bringing up azure but... You might take a look at the azure active directory b2c service. You can use stand alone azure ad or integrate with other various providers (Google, Facebook,etc). Their posted child is the real Madrid website which uses it.