[1.12] Custom Villager/structure spawning

I've created a custom VillagerProfession and VillagerCareer and registered them with VillagerRegistry. They work correctly when I use a spawn egg to summon them, but I haven't run across any "in the wild" in generated villages. I'm assuming I have to create a new village structure in order to spawn my guys.

I've put together a basic StructureVillagePieces.Village class (largely modeled after StructureVillagePieces.Church) just to try and get something to generate in the world before I dig deep into customizing it. Unfortunately, I can't figure out how to add it to the generation process. I assume there's some registry I need to hook my class into, but I haven't been able to find it.