How to log the status changes of a post

[garubi]

I would like to extend the plugin so that I can log when users change the status of a post (Draft, Pending, Published).
I looked at the filters and the source code but I'm really lost.
WP provides the actions need to trigger it: https://codex.wordpress.org/Post_Status_Transitions but how i can i log them?
Some directions, or an example/mockup of the code would be great.

[JJJ]

Check out WP_User_Activity_Type_Posts::transition_post_status().

Basically, I'd appreciate a pull request for the different transition types, so WP User Activity can include support for them out of the box.

Right now, create and future are a little greedy.

[JJJ]

Bumping to 2.1.0.