Wuyi Chen

In Section 9.3, Zuul server, licensing service and organization service will send trace to Zipkin server. Originally licensing service and organization service are integrated with Kafka message queue. So `spring-cloud-starter-stream-kafka`...

For storing users' credentials in DB, the spring security will check `users` table and `authorities` table. But in the book/ the original source code of the book, it uses `users`...

- One-to-One - One-to-Many - One-to-Many: @OneToMany - Many-to-One: @ManyToOne