We can add more authorized paths to authorizedPaths if we need
more resources to be pulled from the NewLeaf/Invidious backend
on the same domain.
This route forwards to the client a few headers like Bibliogram
https://git.sr.ht/~cadence/bibliogram/tree/ea7cd5d5/item/src/site/api/proxy.js#L28-29
so we can also use this route to possibly proxy videos in the
future.
We are strict about the url parameter not overriding the
NewLeaf/Invidious backend (instanceOrigin) by ensuring
fetchURL has instanceOrigin as prefix.
