Background
This story is to update the HPA form to allow users to scale on metrics other than CPU and memory.

Breakdown of HPA UX Enhancements

• Allow users to scale on metrics other than CPU and memory.
  • For all HPA forms, add the ability for users to dynamically input custom metrics to the bottom of the form.
  • Include a popover to describe the metric types available for users to input
  • Link out to documentation to learn more.

Assets

• Design Doc (WIP): https://docs.google.com/document/d/1C-wPkuSNrWheIvYvPeB13jfKgGdUem6kLpfSOJMJDQQ/edit
• Marvel (WIP): https://marvelapp.com/prototype/fj6h5eh

Note from Joel Smith on 2/11: Even though the API is there, hold off on custom metrics until they are at least in tech preview.