Flow to get an image from a pnut.io post oembed

get_pnut_oembed.txt

if the post oembed does NOT have a "url_expires_at" field:

    it's not a pnut file, it's safe to use the "url" field from the post oembed

else:

    if "url_expires_at" is NOT past:

        it's safe to use "url" field from the post oembed

    else:

        if there's a "url_immediate" field:

            use "url_immediate" instead of "url"

        else:

            use "file_id" and "file_token_read" from the post oembed to

            GET /files/{file_id}?file_token_read={file_token_read}

            this gives a new object if the file hasn't been deleted

            and from this new object:

                use the "link" field instead of "url"

                use the "link_expires_at" field instead of "url_expires_at"