As written on the API docs: An Action Provider Widget is a widget that has declared several actions by using its 'public static function actions()'. After, a Controller can easily import all its declared actions on its 'public function actions()'.
I am writing this guide because I struggled to find a resource that included ALL of the necessary steps to completely separate the frontend from the backend. After reading guides like Configuring different sessions for backend and frontend in yii-advanced-app and yii2 configuring different sessions for backend and frontend in yii advanced application template, there are still steps missing. It is funny how the 2nd one says it is an extension of the first one's article. So I guess, my wiki guide here is yet a 3rd and more complete extension of both of them. I also found a few StackOverflow questions and blog posts regarding this topic. None of them fully worked, and must be missing some magic sauce!
We all know how good 'gii' automates the code for us and we normally tend to be happy with what that tool offers at the beginning of our Yii learning curve. But as soon as you start working in larger and larger projects, you realize that its code is too repetitive to maintain and having a small pitfall in general actions means to go over and over through them to fix the issues.
I have had to do this a couple of times now so I figured I would share it with the community. I am going to keep this short because I really hope that you are familiar with jQueryUI's Sortable class before starting this tutorial.