Add a new section after the Hello World walkthrough for additional detail that
doesn't directly apply to this example. Included are discussions on creating
negative tests and handling custom query parameters.
Remaining integration of the material originally for #3478
Fill in additonal detail following the existing document structure.
Includes authentication, custom streams, negative tests, and types
of test data and fixtures. Also fix typos and reformat to match the
new integration doc style.
Partial integration of the material originally for #3478
Breaks out the Hello World example to create a new
webhook-walkthrough.md. Includes minor edits so the two docs
read well. Adds the new page, "Webhook walkthrough", to the TOC.
Fixes#3498
Feorlen