title: Need to size StackView proportionately to my device size
body: <p>I am building my screen in code which contains a stackView that holds my textfields.  This stackView looks great on an iPhone 8/8Plus/X device, but too large on an SE screen.  I realize that I need to size my stackView proportionately to the device size, but am not sure how programmatically.  All the tutorials that I've seen show how to do it in IB.</p>
  
  <p>Here is the code I'm working with:</p>
  
  <pre><code>        let textFieldStackView = UIStackView(arrangedSubviews: [nameTextField, emailTextField, passwordTextField])
          textFieldStackView.translatesAutoresizingMaskIntoConstraints = false
          textFieldStackView.distribution = .fillEqually
          textFieldStackView.axis = .vertical
          textFieldStackView.spacing = 10
  
          view.addSubview(textFieldStackView)
  
          textFieldStackView.topAnchor.constraint(equalTo: logoImageView.bottomAnchor, constant: 100).isActive = true
          textFieldStackView.heightAnchor.constraint(equalToConstant: 150).isActive = true
          textFieldStackView.widthAnchor.constraint(equalToConstant: 350).isActive = true
          textFieldStackView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
  </code></pre>
  
  <p>It's not just the width, but the height as well which I need to grow accordingly.  How would I do this in code?</p>