Get the newest (or oldest) item of another relation

Since Laravel 8.42, in an Eloquent model, you can define a relation that will get the newest (or oldest) item of another relation.

/**
 * Get the user's latest order.
 */
public function latestOrder()
{
    return $this->hasOne(Order::class)->latestOfMany();
}
 
/**
 * Get the user's oldest order.
 */
public function oldestOrder()
{
    return $this->hasOne(Order::class)->oldestOfMany();
}