Unity3D. Building Plugins for Android. Up to date documentation

It’s possible to build native android plugins in Android Studio. It’s possible to use aar files instead of pre-compiled Android library projects. We do this in our game.
But where can I find up to date documentation?
This doc is obsolete Unity - Manual: Create and use plug-ins in Android

@Andrey-Postelzhuk : sorry we didn’t have enough time to get our hands on the documentation. It’s on our todo list though.

As for AARs - you can keep them at any location in your project, they should be detected automatically as an android plugin, and processed accordingly.