Docile Dogs is a small plugin for Spigot (& PaperMC) servers to prevent players from killing tamed dogs.
Download resource from Spigot here and install into your server's /plugin folder
No setup is required. The plugin will prevent damage from ANY PLAYER to ANY TAMED WOLF
Pull requests are welcome, however, as it is intended to be a small lightweight plugin, please raise an issue to discuss your potential changes first!