I need to perform a form POST to a 3rd party payment provider with angular typescript and also do the redirect afterwards. If I do standard form submit through a standard html page the form submit automatically redirects to the 3rd party payment providers hosted payment page, but not when I do a HttpClient.post in angular. 

I looked at observables and and injectors to see if that would help, but nothing I searched and found seemed to solve this specific problem. Though I read so many different problems and solutions between different angular versions I may have lost some obvious answer along the line.

The reason I am not doing a hidden form with hidden fields is because I need to be able to this same thing through a mobile (Ionic) app later, and I will need to use their inbuilt HttpClient along with the normal HttpClient for standard web pages.

```js
import { Component, OnInit } from '@angular/core';
import { HttpClient, HttpHeaders } from '@angular/common/http';

@Component({
  selector    :  'app-paymenttest-page',
  templateUrl :  'paymenttest.page.html',
  styleUrls   : ['paymenttest.page.scss']
})
export class PaymentTestPage implements OnInit {

  constructor(private  http : HttpClient) {
  }

  private void makePayment(url: str, formData: FormData): void {
    let headers = new HttpHeaders({'Accept' : 'text/html' });

    this.http.post(url, formData, {
      headers         : headers,
      responseType    : 'text',
      })
       .subscribe(
         (res) =>  {
           console.log('post res');
           console.log(res);

           window.location.href = res.url;
    // How do I simulate a form submit redirect with res.body here?
         },
         (err) => {
          console.log('post err');
          console.log(err); 
      });
  }
}

```

I expect to be able to do a 3rd party hosted page redirect, but all I am getting back is the html text response from the 3rd party. Which I also get when doing a plain html form submit, but somehow the plain html form submit also handles the redirect.

-- Edit
The response I am getting is the actual HTML payload from the URL that I am posting to and is expecting to be served from that URL. So the question is how does a standard html form submit navigate to the POST url and serve the returned content from there?