docs: protected InputStream getBase64DecodedMessage(HTTPInTransport transport) throws MessageDecodingException {
          log.debug("Getting Base64 encoded message from request");
          String encodedMessage = transport.getParameterValue("assertion");
  
  
          if (DatatypeHelper.isEmpty(encodedMessage)) {
              log.error("Request did not contain either a SAMLRequest or "
                            + "SAMLResponse paramter.  Invalid request for SAML 2 HTTP POST binding.");
              throw new MessageDecodingException("No SAML message present in request");
          }
  
          log.trace("Base64 decoding SAML message:\n{}", encodedMessage);
          byte[] decodedBytes = org.apache.commons.codec.binary.Base64.decodeBase64(encodedMessage.getBytes(StandardCharsets.UTF_8));
          if(decodedBytes == null){
              log.error("Unable to Base64 decode SAML message");
              throw new MessageDecodingException("Unable to Base64 decode SAML message");
          }
  
          log.trace("Decoded SAML message:\n{}", new String(decodedBytes));
          return new ByteArrayInputStream(decodedBytes);
      }