fix(openapi): add missing ad-hoc webhook fields to WebhookRepresentation

[vdusek]

Description

• The WebhookRepresentation schema (items of the Base64-encoded webhooks query parameter on the run/build endpoints) declared only eventTypes, requestUrl, payloadTemplate and headersTemplate, but the platform accepts and honors more fields for ad-hoc webhooks: the run-start handler spreads each webhook object into the same insertWebhook path used by the create-webhook endpoint, including the idempotencyKey dedup logic.
• This adds the missing idempotencyKey, ignoreSslErrors and doNotRetry properties to the schema, so generated API clients (e.g. apify-client-python) stop dropping them.
• The Python client and SDK changes that build on this:
  • fix: forward idempotency_key, ignore_ssl_errors and do_not_retry in ad-hoc webhooks apify-sdk-python#963
  • fix: add idempotency_key, ignore_ssl_errors and do_not_retry to generated webhook models apify-client-python#855

[apify-service-account]

✅ Preview for this PR (commit bba5e14) is ready at https://pr-2640.preview.docs.apify.com (see action run).

[apify-service-account]

Important

Action required — @vdusek please coordinate this docs PR with the Python API client PR linked below.

Because this PR modifies the OpenAPI specification, the generated models in apify-client-python must be regenerated to stay in sync. This has already been done automatically:

A companion PR has been opened in apify-client-python with the regenerated models: apify/apify-client-python#855

• Please make sure to review and merge both PRs together to keep the OpenAPI spec and API clients in sync.
• You can ask for review and help from the Tooling team if needed.