forwarding/proxying a request using RestRserve

Question

Suppose I have the following setup, which has two apps running on different ports using the RestRserve (these might e.g. be on different servers, both of which I control). I would like requests to :8081/health to be forwarded to :8080/health exactly as is, to get the response, and to return the response back to the client. I also need to pass it all the query string variables, etc - the request should look identical, except for the swap of the base URL, so that any request to (say) http://localhost:8081/health is identical to a request to http://localhost:8080/health.

What's the best (simplest/clearest/most robust) way to achieve this?

library(RestRserve)
app1 = Application$new()
app2 = Application$new()
  
app1$add_get(
  path = "/health", 
  FUN = function(.req, .res) {
    .res$set_body("OK 1!")
  })

app2$add_get(
  path = "/health2", 
  FUN = function(.req, .res) {
    .res$set_body("OK 2!")
  })

app2$add_get(
  path = "/health", 
  FUN = function(.req, .res) {
    # Code here to forward request to app1, get result, and then pass back to client
  })

backend = BackendRserve$new()
backend$start(app1, http_port = 8080, background = TRUE)
backend$start(app2, http_port = 8081)