FIX: Redirects containing Unicode usernames didn't work (PR #9989)

@eviltrout I wonder if we should remove the following two routes. I couldn’t find any references in our code. AFAIK we are always using the /my/... routes.

https://github.com/discourse/discourse/blob/0f09fd22f3afa6ba22499e2fbf6d50a4574831aa/config/routes.rb#L318

https://github.com/discourse/discourse/blob/0f09fd22f3afa6ba22499e2fbf6d50a4574831aa/config/routes.rb#L377

I didn’t even know that /email_preferences and /user_preferences were a thing. They exist since the beginning of the project.

GitHub

Sure, if you’ve searched through and found them missing I don’t see why not!

@eviltrout Thanks for the review. I’m mentioning you because I updated the PR to fix the usernames in avatar redirects and I added a commit to remove the unused routes.