...It is built on Spring Boot 3.x and Java 21, and includes integrations such as Spring Security 6.x, JPA (via Hibernate) for persistence, and Redis for session/token management. The goal is to show how to migrate from stateful, session-based auth toward stateless, modern REST API authentication using JWTs, roles, and permission checks. The code covers typical flows like user registration, login, logout, refreshing or invalidating tokens, and endpoint authorization with annotations like @PreAuthorize. It’s cleaner and more up-to-date than many older tutorials, reflecting current Spring and Java versions and allowing direct experimentation by developers.