void RenderingSystem::attachController(unsigned int EntityKey, EntityID entity)
{
    // layer is an enum/int
    auto layer = mProperties.get<P::Visible>(entity)->layer;
    auto controller = new RenderingController(entity, mProperties);
    // mControllers is an array of maps
    mControllers[layer][EntityKey] = std::unique_ptr<RenderingController>(controller);
}