PhoenixRecipes is a Bukkit plugin turned Minecraft Data Pack that adds some custom recipes to the server.
Once Horses were added to Minecraft, it quickly became apparent how rare Saddles and Horse Armour were. First a plugin was found and added to give the ability to craft horse armour. Which plugin exactly is lost to history, but it thought to be one of these(in order of release):
After the plugin fell out of support, had constant errors in the console, but miraculously still worked, I decided to recreate it for the most up to date Bukkit versions, added NameTags, Chainmail armour, Elytra as time went on.
In 2018, the plugin was replaced with a Minecraft Data Pack as it was less prone to being broken by updates, easier to manage, and not dependent on the Bukkit API.