How to redirect HTTP response from 3party to client without change

help
1

Hello,
My meteor app is connected with a microservice. (Authentification with token).
At some point, my user click on a button, it triggers a method, which do a HTTP.call :

// Event on client :
  'click .js-my-export': function (event, templateInstance) {
    event.preventDefault();
    ...
    Meteor.call('exportMyPDF', options, (err, res) => {
      if (err) console.log(err);
      const blob = new Blob(
        [res.content],
        { type: `${res.headers['content-type']};base64` }
        // { type: 'application/octet-stream;' }
      );
      const fileURL = URL.createObjectURL(blob);
      window.open(fileURL);
      // saveAs(blob, 'mydoc.pdf');
    });
  },
// On server :
export function exportMyPDF(...) {
  const options = ...;
  return HTTP.call('GET', `microservice_url/api/exports/mypdf`, options);
}

However it didn’t works, when I go directly to the microservice route with my navigator or postman I got the response without problems. ( A pdf with some content ). So I have the feeling that I am not doing the redirection nicely with meteor, something, somewhere is corrupted, is return HTTP.call a good solution ?
If it can helps here is the response from the server ( console.log(res) ) : { res : Object } printed in the console:

content: "%PDF-1.4↵1 0 obj↵<<↵/Title (��)↵/Creator (��)↵/Prod ..... lots of characters....%"
data: null,
statusCode: 200,
headers: {
  connection: "close",
  content-disposition: "attachment; filename=myDoc.pdf"
  content-type: "application/pdf",
  date: "date",
  transfer-encoding: "chunked",
  x-powered-by: "Express"
}