YAPP is a Bukkit plugin developed by @nisovin . I personally used this plugin for my permission managing for many years, however it soon became outdated.
I finally got around to fixing the source code to work with the version of Spigot I'm now using, and figured I'd publish the source code for anyone else who found this plugin as useful as I did.
This has been lightly tested to work on Spigot-1.13.2-RC0.1.
Nisovin wrote pretty much all of the code here, I just modified it to work again. Here's the original dev.bukkit.org project page.
I'm bad at writing README files so here's the TL;DR, all credit for the original plugin goes to @nisovin , I updated the plugin from MC 1.6.2 (v 1.4) to MC 1.13.2 (v 1.4.1).