src/FACTFinder/Adapter/ProductCampaign.php
public function addProductNumbers($productNumbers)
    {
        $parameters = $this->request->getParameters();
        $parameters->add('productNumber', $productNumbers);
        $this->upToDate = false;
    }
public function addProductNumbers($productNumbers)
    {
        $parameters = $this->request->getParameters();
        $parameters->add('productNumber', $productNumbers);
        $this->upToDate = false;
    }
Add one or multiple product numbser to get campaigns for, in addition to any
numbers previously set.

@param string|string[] $productNumbers One or more product numbers.