public function getIdAttribute($value = null)
{
    // If we don't have a value for 'id', we will use the MongoDB '_id' value.
    // This allows us to work with models in a more sql-like way.
    if (! $value && array_key_exists('_id', $this->attributes)) {
        $value = $this->attributes['_id'];
    }

    // Convert ObjectID to string.
    if ($value instanceof ObjectID) {
        return (string) $value;
    }

    if ($value instanceof Binary) {
        return (string) $value->getData();
    }

    return $value;
}

public function accessToken(): HasOne
{
    return $this->hasOne(AccessToken::class, 'userId', '_id');
}

// Convert ObjectID to string.
if ($value instanceof ObjectID) {
    return (string) $value;
}