Building a custom webform handler

In this session we will look at how to build a webform as well as how to create a custom webform handler to integrate the webform with a legacy payment system (Nelnet's QuikPAY).

We will see some brief examples about:
- How to define a webform handler.
- How to implement a server side webform validation.
- How do controller, route and template play together.
- How/When/Why to set, get, and remove a session variable
- How to take advantage of (abuse?) the Computed Twig field in webform.
- Use Drupal Console and PHPStorm to enhance your module development experience.

At the end of this session, you'll walk away with a better understanding of webform handlers and how to build one when you need to.