Resolved How to use Unity IAP 4.4 with Unity 2019

I got a deprecated warning from Google that I must use Billing library version 4. After some research, Unity 4.4.0 uses billing library 4, but in my package manager, the last available version is 4.1.5. Note that I'm using 2019.4.3f1.

I don't want to upgrade Unity to a newer version, it always causes tons of trouble, glitch, crash, and malfunctions, and I just keep using this version. How do I use Unity IAP 4.4 .0in 2019?

 

This is really a shame, I'm sorry to say this guys, but for me it's the same S***. Now I have to upgrade my whole Animation-System, because I used Anima2d for all my Animations, only because you guys don't want to integrate IAP 4.4. Anima2D was connected with my shop, my server backend, skins of my players and throughout the whole game, and now I have to start off at the beginning with all this. I really don't understand why you guys are making it so hard for us developers with all those continuous update-S*** really. Some months ago I had to upgrade to 2019 because of Plastic SCM, and now this. Thank you Unity-Guys for making my life so hard.