private function findCustomer($mail)
    {
        $customerResult = $this->client->request('GET', 'accounts/contacts', [
            'contactEmail' => $mail,
        ]);

        if (empty($customerResult)) {
            return null;
        }

        $possibleCustomers = array_filter($customerResult, function ($entry) {
            return $entry['singleAccess'] !== '1';
        });

        if (empty($possibleCustomers)) {
            return null;
        }

        return array_shift($possibleCustomers);
    }
private function findCustomer($mail)
    {
        $customerResult = $this->client->request('GET', 'accounts/contacts', [
            'contactEmail' => $mail,
        ]);

        if (empty($customerResult)) {
            return null;
        }

        $possibleCustomers = array_filter($customerResult, function ($entry) {
            return $entry['singleAccess'] !== '1';
        });

        if (empty($possibleCustomers)) {
            return null;
        }

        return array_shift($possibleCustomers);
    }
@param string $mail

@return null|array