We have an existing legacy system (spring controllers and pojo’s running in tomcat against a postgres backend) that uses a home-grown authentication and authorization system and we would like to join the 21st century and transition to a OpenID/Oauth IDP such as Keycloak. We have 10s of thousands of pre-existing users.
Are there any HOWTOs or videos that describe some recommendations as to how to accomplish this most successfully? Thanks in advance for any help and/or suggestions. Much appreciated.