Missing REST endpoint to obtain a populated form.

The current REST API supports getting an initial form for some properties, and "triggering" callbacks to update the form according to changes from the user.

There is currently no way to save the properties, then re-obtain the current form used to edit it later.

For example, if you have one property (`useKerberos`, default false) that controls the visibility of another (`kerberosPrincipal`, default empty, only shown when `useKerberos` is true).

When you have saved the properties:

{
  "useKerberos": true,
  "kerberosPrincipal": "user@BIGDATA.COM"
}

There is no POST endpoint that takes the saved properties and returns the form with the `kerberosPrincipal` field visible.