code: public function whitelist(string $address): WhitelistResponse
      {
          try {
              $response = $this->callHydroApi(
                  'post',
                  'whitelist',
                  [
                      'timeout' => 60,
                      'json' => [
                          'address' => $address
                      ]
                  ]
              );
  
              $data = \GuzzleHttp\json_decode($response->getBody()->getContents(), true);
          } catch (RuntimeException $e) {
              throw AddressWhitelistingFailed::forAddress($address, $e->getMessage());
          } catch (InvalidArgumentException $e) {
              throw AddressWhitelistingFailed::forAddress($address, $e->getMessage());
          } catch (GuzzleException $e) {
              throw AddressWhitelistingFailed::forAddress($address, $e->getMessage());
          } catch (ApiRequestFailed $e) {
              throw AddressWhitelistingFailed::forAddress($address, $e->getMessage());
          }
  
          return new WhitelistResponse(
              $data['hydro_address_id'],
              $data['transaction_hash']
          );
      }
docs: All users who want to access to your Raindrop-enabled system will have to be whitelisted.
  
  @param string $address Hydro Etherium Address
  @return WhitelistResponse
  @throws AddressWhitelistingFailed