title: URLSession returns HTTP 403 error page
body: <p>I'm trying to run a HTTP Request in Swift, to POST 2 parameters to a URL. 
  But it always returns 403 error page, what's wrong?</p>
  
  <p>I trying adding Content-type header, but it doesn't work.</p>
  
  <p>Code:</p>
  
  <pre><code>    print("ENVIAR DATOS")
  
      let url = NSURL(string: "https://www.portaljuridico.com.co/portaljuridico/User/login")
  
      let request = NSMutableURLRequest(url: url! as URL)
      request.httpMethod = "POST"
  
      let param = ["username" : "juan", "password" : "123"]
      guard let httpBody = try? JSONSerialization.data(withJSONObject: param, options: []) else { return }
  
      //request.addValue("application/form-data", forHTTPHeaderField: "Content-Type")
      //request.setValue("application/json", forHTTPHeaderField: "Content-Type")
      //request.addValue("application/json", forHTTPHeaderField: "Accept")
      request.httpBody = httpBody
  
      let task = URLSession.shared.dataTask(with: request as URLRequest) { data, response, error in
          guard let data = data, error == nil else {
              print("error = \(error!)")
              return
          }
  
          if let httpStatus = response as? HTTPURLResponse, httpStatus.statusCode != 200 {
              print("statusCode should be 200, but is \(httpStatus.statusCode)")
              print("response = \(response!)")
          }
  
          let responseString = String(data: data, encoding: .utf8)
          print("responseString = \(responseString!)")
      }
  
      task.resume()
  </code></pre>