Adds a `request` key to the webhook data if a request is associated with the origination of the webhook.
Note: We're not attaching a complete representation of the request in the interest of both security and brevity.
Clarify webhook context variable names and event types.
Replace `model` with `object_type`, update event values to match actual
output (`created` vs. `create`), and refresh example JSON to reflect the
current API response format, including new fields like `display` and
`display_url`.
Fixes#21489
* Add searchable deprecation comments on request_id and username fields in EventContext
* Add deprecation note in webhooks documentation
* Expand deprecation note/warning
* Add version number to deprecation warning
* Add deprecation warning to two other places
