Create ChatGPT Ads Conversion Event

Creates a ChatGPT Ads conversion event setting (which tracked action counts as a conversion) on one pixel source.

`event_type`: one of OpenAI's standard events — appointment_scheduled, lead_created, order_created, registration_completed, subscription_created, trial_started, checkout_started, items_added, contents_viewed, page_viewed, app_installed, app_opened — or `custom` with `custom_event_name` (lowercase letters, digits, _ or -, up to 64 characters, not a built-in name). `source_id` is the pixel source id (cds_…) from chatgpt_ads_conversion_setup; left empty it uses the account's only source. The attribution window is 30 days, as OpenAI requires. A setting does not send events by itself (the site's pixel or server sends that event), and only a STANDARD event can be the goal of a conversions-objective campaign. Attach it to campaigns with update_chatgpt_ads_campaign. confirm=false returns a dry run.