Parse topic permalinks #5866
Description
When parsing an internal link, we should handle the upcoming "topic permalink" feature:
In the current draft, these look like /with/NNNN, with a message ID.
Currently the app doesn't interpret the "anchor" meaning of /near/ links at all (that's #3604) — we already effectively give /near/ links exactly the meaning that the upcoming /with/ links will have. So to handle the new links, we just need to parse them and then handle them the way we already handle /near/ links.