I was seeing duplicate endpoints appearing under each module (typically
2 of each). This turned out to be due to the `render-operation` partial
being called multiple times (once when rendering the page, and another
when rendering the left-hand-side TOC).
We now check whether the endpoint has already been added to the list
before insertion, via a "seen" map (for quick lookup).
Any endpoint in a CS API module was not getting listed. This is because they are stored in nested pages. We need to hoist them up to the outer page, such that they can be retrieved and rendered by our endpoints TOC partial.
