downloadFile method
Implementation
@override
Future<void> downloadFile(String url, Map<String, dynamic> body) async {
http.Response response = await http.post(
Uri.parse(url),
body: body,
);
var blob = html.Blob([response.bodyBytes], response.headers["content-type"], "native");
html.AnchorElement(href: html.Url.createObjectUrl(blob).toString())
..setAttribute("download", "report.xlsx")
..click();
}