title: I can create spring-boot stater without spring.factories, why?
body: <p>In the spring-boot guide <a href="https://docs.spring.io/spring-boot/docs/current/reference/html/boot-features-developing-auto-configuration.html" rel="nofollow noreferrer">Creating your own auto-configuration</a>, It is mentioned that I have to create a META-INF/spring.factories file and put something under the EnableAutoConfiguration key. But I've created a starter without this file and it works well when a project is using it. Do you know why it works? Does it mean this file is optional? </p>