Company.php

<?php

namespace Titan\Model;

use Titan\Model\TitanModel;
use Illuminate\Database\Eloquent\Model;
use Titan\Model\JsonTransformer\Company as Transformer;
use Titan\Model\Address;

class Company extends Model
{
    use TitanModel;

    public $timestamps = false;
    protected $table = 'company';
    public function qbCustomer()
    {
        return $this->hasOne(\App\Modules\QuickBooks\Model\Customer::class, 'qb_id', 'qb_id');
    }
}

CompanyTransformer.php

<?php

namespace Titan\Model\JsonTransformer;

use Titan\Model\Company as Model;
use League\Fractal\TransformerAbstract;
use League\Fractal\ParamBag;

class Company extends TransformerAbstract
{

    /**
     * List of resources possible to include
     *
     * @var array
     */
    protected $availableIncludes = [
        'address',
        'brand',
        'category',
        'collateral',
        'contact',
        'email',
        'event',
        'location',
        'notification',
        'note',
        'phone',
        'status',
        'summary',
        'url',
        'viewedLine',
        'personCompany',
        'storeTypes',
        'storeType',
        'emailType',
        'phoneType',
        'qbCustomer',
    ];

    /**
     * @param \Illuminate\Database\Eloquent\Model $company
     * @return array
     */
    public function transform(Model $company)
    {
        return [
            'id'                => (int) $company->id,
            'name'              => $company->name,
            'status'            => $company->status,
            'options'           => $company->options,
            'other'             => $company->other,
            'qb_id'             => $company->qb_id,

            '_links'   => [
                [
                    'rel' => 'self',
                    'uri' => '/api/v1/data/company/'.$company->id,
                ]
            ],
        ];
    }
    /**
     *
     * @param Model $model
     * @param \League\Fractal\ParamBag $params
     * @return \League\Fractal\Resource\Collection
     */
    public function includeQbCustomer(Model $model, ParamBag $params = null)
    {
        return $this->item($model->qbCustomer, new \App\Modules\QuickBooks\Transformer\Customer, 'qbCustomer');
    }
}