Output format for preview renders when include_preview is true. 'url' returns preview_url (iframe-embeddable URL), 'html' returns preview_html (raw HTML). Ignored when include_preview is false or omitted.
Output format for preview renders when include_preview is true. 'url' returns preview_url (iframe-embeddable URL), 'html' returns preview_html (raw HTML). Ignored when include_preview is false or omitted.