How should I implement proxying and redirects on the app platform?

I’d like routes like /wiki and /forum to pass traffic through to another website (on another host), so it looks to users like they’re on the same domain. I also have a number of redirects, e.g. /xyz redirects to a separate domain to maintain old links.

I currently implement these all in nginx, and “everything else” is proxied to my rails app.

In the DO app platform world, I assume I should use the rails router for redirects, but what about proxying? Should I use rack proxy or something? Or is there some way to control routing at a higher layer in the app platform (e.g. via some ingress container)