I have existing Spring Boot application with Spring Security 5 and OAuth2 client, I've successfully configured authentication with external OAuth2 provider (GitLab, in my case).
Now I have problem with configuring authorization. I'd like to have some method that would let me write code to resolve roles for given user (either by making a call to the database or just checking hard-coded username).
I've found out that it could be achieved by using PrincipalExtractor and AuthoritiesExtractor, described in a nice article. However, those classes are no longer present in recent Spring Security. What is an alternative way to achieve that, compatible with Spring Security 5?