item namespace with datapacks?

a while back someone in one of the discord servers I'm at asked if it was possible to add custom namespaces for items in minecraft (the stuff shown in advanced tooltip like minecraft:stone_pickaxe). We didn't exactly know if it was really possible and from my knowledge, these items are hard coded into the game's enumeration files. This however didn't stop us from thinking since it was from a server of one of the popular datapacks out there. so my question is, are datapacks capable of adding new items into minecraft's registry?