How to get a list of all possible names?

I'd like to make an interface where someone can start typing a name and search for matches, but I can't find a way to query possible names or to even get a list. The best I can do is search CRs for someone who's used that name and then link back to the person resource they use. There has to be a better way, right? How can I get a list of possible names?

Person Resource = https://<host>:9443/jts/users/<username>

Can't query https://<host>:9443/jts/users