WIP: Webform Handler

[TessaBakker]

Using the 'default' types in Commerce is not always desirable.
Therefore a Webform Handler could be very useful.

This is still in progress, and not ready to merge.

ToDo:

1. Allow to redirect to Cart instead of Checkout Flow
2. Add more configuration
3. Fix the multiple todo's in code
4. Cleanup old code
5. Set 'secure token' option in Webform config when saving the handler

New features:

1. Webform handler for configuration per webform
2. Post validation event for submitting the submission on early leave within the offsite payment provider
3. Optional selection of a calculated order item, by using a Twig computed field

Diagram to explain some inner workings:

Feedback is always welcome!

Thanks to @Sutharsan for feedback and contributions to the code.

[chx]

How this is coming along?

[TessaBakker]

Hi @chx,

I moved the code to drupal.org/project/webform_product to get more support, with some small success :)

Tenken has send me some modifications to the code. I still need to find some time to review and patch them.