There are a few issues with the other solutions I originally used that I found from other wikis. I address the issues I had in this much simpler and shorter way. I am also going to explain what is going into way more detail than others to help people understand what's going on.
If you develop rather complex applications with Yii2, you might already be familiar with yii2-app-advanced application template. Well, the template is awesome and provides high flexibility regarding code/configuration sharing among parts of an application.