dynamic allows on-the-fly creation of registration codes

Fixing coding standard issues.

Patch didn't attach, trying again.

Missed a couple. Hopefully this one is good.

Here is an example of how to use this on your site:

In a custom module create a services file (ex. - mymodule.services.yml) file and an event subscriber (ex. - src/Event/MyModuleRegcodeSubscriber.php):

services:
  mymodule.regcode_subscriber:
    class: Drupal\mymodule\Event\MyModuleRegcodeSubscriber
    tags:
      - { name: 'event_subscriber' }

<?php

namespace Drupal\mymodule\Event;

use Drupal\regcode\Event\RegcodeValidateEvent;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;

class MyModuleRegcodeSubscriber implements EventSubscriberInterface {

  /**
   * {@inheritdoc}
   *
   * @return array
   *   The event names to listen for, and the methods that should be executed.
   */
  public static function getSubscribedEvents() {
    return [
      RegcodeValidateEvent::REGCODE_VALIDATE => 'updateRegcode',
    ];
  }

  /**
   * React to a regcode validate event.
   *
   * @param \Drupal\regcode\Event\RegcodeValidateEvent $event
   *   Regcode validate event.
   */
  public function updateRegcode(RegcodeValidateEvent $event) {
    $user_code = $event->getUserEnteredRegcode();
    $db_code = $event->getRegcode();

    // Only react if the code isn't in regcode db table.
    if (!$db_code) {
      // Check if code is valid.
      if ($this->checkRegcode($user_code)) {
        // Create code on the fly.
        $code = new \stdClass();
        $code->code = $user_code;
        $event->setAndSaveAlteredRegcode($code);
      }
    }
  }

  /**
   * Validate the code.
   *
   * @return bool
   *   TRUE or FALSE if the code is valid.
   *
   */
  private function checkRegcode($code) {
    // Put custom validation code here.
  }

}