Create a new engagement news article

Create a news article for a project. subject is required, either as { localized: { en: "..." } } or as a bare per-language map { en: "..." } (canonicalized server-side; same for message and markdownMessage). sender defaults to the authenticated user and trigger defaults to sessionStarted/firstoccured when omitted. Instead of message you may send markdownMessage (localized markdown), which is converted to rich text server-side. searchContent is computed server-side and ignored if supplied. Creating a CHANGELOG news item with status: "live" immediately sends changelog notification emails to subscribers. News items always use a dynamic audience: frequencyType: "fixed" and csvContacts are ignored. Target people with targetAudience and conditions instead.