Keycloak is one of great identity server that exist. It's opensource, and free also, by the way if you need professional support you can achieve that from Redhat.
In the Microservice paradigm, we split each business into a service, and one of important business is user management. Keycloack handle it for your system and also help your service to be secure.
Now I want share some common endpoint of Keycloak, to make your job easier.