Are there ready-made user models on API (HTTP) with registrations and authorizations?

Question

API

On most projects, registration (authorization) of users is required, and on most by e-mail. Are there any services that provide a registration/authorization API? And is there a need for them?

Answer 1

The main task of the services is the distribution of computing power, therefore, for example, analytics services are very necessary, the application can send data with each user action, and this is a huge load on the server and many records in the database, it is cheaper to rent a service specifically for analytics than a "bicycle".
Registration is too small a proportion of the load and on the disk, rather libraries and development tools are needed to speed up implementation, in fact, there is a rather large "gap" between CMS and frameworks, it would be filled with your product, but this gap must be seen at the same time to be able to deal with such large-scale projects is an extremely rare combination.
It is with registrations - I don’t know, all social networks have an API, this is for authorization without the need to register if you already have an account on a social network, but it’s important without the need for registration.