It used to fetch it from /site.json, but /categories.json is the more
appropriate one. This one also implements pagination, so we have to do
one request per page.
This persona searches Discourse Meta for help with Discourse and
points users at relevant posts.
It is somewhat similar to using "Forum Helper" on meta, with the
notable difference that we can not lean on semantic search so using
some prompt engineering we try to keep it simple.