Author: Adam Piotrowski (adam@wellcommerce.org)
 protected function filterConfiguration(array $configuration, PaymentProcessorInterface $processor) : array
 {
     $supportedConfigurationKeys = $processor->getConfigurator()->getSupportedConfigurationKeys();
     return array_filter($configuration, function ($k) use($supportedConfigurationKeys) {
         return in_array($k, $supportedConfigurationKeys);
     }, ARRAY_FILTER_USE_KEY);
 }
 public function add(PaymentProcessorInterface $processor)
 {
     $this->items[$processor->getConfigurator()->getName()] = $processor;
 }