Provide an "upsert" route that allows for add/edit a config page type

Problem/Motivation

When creating custom link for editors to change the fields of the config page I want them to be unaware of whether they are creating it for the first time or editing. Right now I need to create an empty config page and point the link to edit that config page.

Proposed resolution

It can be as simple as a redirect to add or edit depending on if there is already a config page created for a bundle

Remaining tasks

Code