Retrieve generated carousel files

Returns the output of a completed post. Call only after status is COMPLETED. For responseType PNG, result.data is an array of image URLs (one per slide); for PDF, result.data is a single document URL; for MP4, result.data is a single video URL. Docs: https://postnitro.ai/docs/embed/api/post-output.md A VIDEO post's result also has duration, in seconds. A video longer than 2:00 fails as an MP4, after its design is saved: the 400 then gives the error with the video's duration and the design's designId and editorUrl, to shorten it in the editor.