code: public function execute()
      {
          $result = $this->resultJson->create();
  
          try {
              $activeVersion = $this->getRequest()->getParam('active_version');
  
              $dictionary = $this->api->getAuthDictionary($activeVersion);
  
              if ((is_array($dictionary) && empty($dictionary)) || !isset($dictionary->id)) {
                  return $result->setData([
                      'status'    => 'empty',
                      'msg'       => 'Authentication dictionary does not exist.'
                  ]);
              }
  
              $user = $this->getRequest()->getParam('auth_user');
              $pass = $this->getRequest()->getParam('auth_pass');
              $key = base64_encode($user . ':' . $pass);
              $this->api->upsertDictionaryItem($dictionary->id, $key, true);
  
              return $result->setData(['status' => true]);
          } catch (\Exception $e) {
              return $result->setData([
                  'status'    => false,
                  'msg'       => $e->getMessage()
              ]);
          }
      }
docs: Create auth item
  
  @return \Magento\Framework\App\ResponseInterface|\Magento\Framework\Controller\Result\Json|\Magento\Framework\Controller\ResultInterface