FIX: improve Vanilla importing (PR #10478)

Hi! I’m working on importing a reasonably large Vanilla Forum into Discourse (self-hosted) and I noticed that some information was getting lost when using script/import/vanilla_mysql.rb. I added them to my own import script, and would like to push those changes upstream.

Here’s what I changed:

I left these features as separate commits to make reviewing easier, but I can squash them if that’s better, please let me know.


I’m seeing that the Javascript Linter task is broken on master since, so I’ll rebase my branch to the commit before that, to be able to see if my changes pass linting.

The JS linter is still broken, I guess I’ll wait until it’s fixed on master. Anyway this PR doesn’t have any JS changes and the other linters and checks do pass.

I rebased master with the linting fix and now all checks are passing :tada:

Thanks for all these improvements, and for adding tests. The rich parser is hard to review, so the tests are helpful.