ロード時にLaravel Eloquentモデルにカスタム属性を追加するにはどうすればよいですか?

<code class="php">public function index()
{
    $sessions = EventSession::all();
    foreach ($sessions as $i => $session) {
        $sessions[$i]->available = $session->getAvailability();
    }
    return $sessions;
}</code>

<code class="php">class EventSession extends Eloquent {

    protected $table = 'sessions';

    public function availability()
    {
        return new Attribute(
            get: fn () => $this->calculateAvailability()
        );  
    }
}</code>

<code class="php">class EventSession extends Eloquent {

    protected $table = 'sessions';
    protected $appends = array('availability');

    public function getAvailabilityAttribute()
    {
        return $this->calculateAvailability();  
    }
}<p><strong>オプション 2: toArray() メソッドをオーバーライドする</strong></p>
<p>または、toArray() メソッドをオーバーライドして属性を手動で設定することもできます。 </p>
<pre class="brush:php;toolbar:false"><code class="php">class Book extends Eloquent {

    protected $table = 'books';
    
    public function toArray()
    {
        $array = parent::toArray();
        $array['upper'] = $this->upper;
        return $array;
    }
    
    public function getUpperAttribute()
    {
        return strtoupper($this->title);    
    }

}</code>

<code class="php">class Book extends Eloquent {

    protected $table = 'books';
    
    public function toArray()
    {
        $array = parent::toArray();
        foreach ($this->getMutatedAttributes() as $key)
        {
            if ( ! array_key_exists($key, $array)) {
                $array[$key] = $this->{$key};   
            }
        }
        return $array;
    }
    
    public function getUpperAttribute()
    {
        return strtoupper($this->title);    
    }

}</code>