Enable nested exposure of Children and Parents

Siblings to come. Just working out some kinks

try router.crudRegister(for: Todo.self) { controller in
    try controller.crudRegister(at: "owner", forParent:  \.owner)
}
try router.crudRegister(for: User.self) { controller in
    try controller.crudRegister(forChildren: \.todos)
}
try router.crudRegister(for: Tag.self)