All gold items have 'mending' by default, and they will no longer be compatible with the mending enchantment. The mod also makes it so that the gold pickaxe has iron level mining.
This mod can be used server side only, but for iron level mining to have the correct mining speed on the client, the mod will need to be installed client side as well. Regardless, it is completely playable sever side only.
You can add this behavior to any item using the #mendablegold:mendable tag if you so choose.
Discord: https://discord.gg/SD2B8kM