code: protected boolean invokeAuthenticationPreProcessors(final AuthenticationTransaction transaction) {
          LOGGER.trace("Invoking authentication pre processors for authentication transaction");
          val pops = authenticationEventExecutionPlan.getAuthenticationPreProcessors(transaction);
  
          final Collection<AuthenticationPreProcessor> supported = pops.stream()
              .filter(processor -> transaction.getCredentials()
                  .stream()
                  .anyMatch(processor::supports))
              .collect(Collectors.toList());
  
          var processed = true;
          val it = supported.iterator();
          while (processed && it.hasNext()) {
              val processor = it.next();
              processed = processor.process(transaction);
          }
          return processed;
      }
docs: Invoke authentication pre processors.
  
  @param transaction the transaction
  @return the boolean