Service Container:
https://laravel-china.org/articles/789/laravel-learning-notes-the-magic-of-the-service-container
https://www.cnblogs.com/lyzg/p/6181055.html
Service Container, Service Provider, Contracts and Façade
https://www.jianshu.com/p/64e8dd779f54
Note: Service Provider 的主要功能就是用来绑定接口的。当然，也可以用来绑定一些其他的东西