Investigate treatment of whitespace in route parameters

[paulmelnikow]

Brought to our attention via a production bug #4982: at least this badge accepts trailing spaces in the route parameter. A brief discussion ensued at #4983 (comment).

I imagined, and still do, that most of our routes should be limited to characters like A-Za-z0-9_-. Most usernames, project names, etc. cannot include whitespace.

We may want to think about a global change to the default route-component regex, with overrides in places where whitespace is acceptable.