First webhook

[stevekrouse]

This is just a stub of a PR.

The problem it's solving is that folks sometimes are actively looking for the word "webhook" when they come to val town with a problem, and I want to capture that energy and funnel it correctly.

I want to help folks parse GET params, POST body form data or json, reply back with OK, and if only POST, handle GETs too. And help the user test things out, etc. Basically best practices for webhooks.

Relevant similar docs:

• https://docs.val.town/guides/creating-a-webhook/#_top
• https://docs.val.town/integrations/github/receiving-a-github-webhook/

[stevekrouse]

In a recent user onboarding call, we copied over some test JSON from a webhook provider's docs into the file and then created a synthetic request to call the endpoint in that same file as a test, and would run it with cmd+enter. This is a nice workflow to have it all in one file, but it's confusing:

1. There's no run button on HTTP vals, so if you don't know about cmd+enter you don't have a way to do this. It's also confusing about when this code that's not in the handler runs. How do we teach folks this runs once on worker startup but not on every request?
2. On save we refresh the GET iframe, which is noisy and confusing
3. Ideally we want this test-case code to live in another file and only run it sometimes, ie when you want to test things out or you want your automated tests to run. How do we help folks set that up in a way that also keeps the feedback loop fast, so you can quickly change things and have the new test case run on keyboard shortcut?