* $order->belongsTo(Customer::class, 'customer_id') * ); */ public function boot(): void { Invoice::resolveRelationUsing('client', function (Invoice $invoice) { return $invoice->belongsTo(Client::class, 'client_id'); }); Client::resolveRelationUsing('invoices', function (Client $client) { return $client->hasMany(Invoice::class, 'client_id'); }); } }