Create or update a recommended articles list

Create a new recommended articles list or update an existing one. Requires Administrator privileges.

Body Parameter Guidelines:

• name: Curated list title or label (e.g. "Editor's Choice").
• placement_area: Target UI layout region (e.g. main_feed, sidebar_top, onboarding).
• expires_at: ISO 8601 timestamp after which the list recommendation automatically expires.
• user_id: Owner/curator numeric user ID.
• article_ids: Staged array of numeric article IDs to include in the recommendation sequence.