Convert from single upstream to multi upstream

BryanDavisrequested to merge
work/bd808/multiproxy into main

The original implementation created a 1 upstream / 1 deployment coupling. This would be a horizontally scalable solution except for the implementation detail that configuration of the deployment used a fixed set of envvars. To enable multiple proxies in a single tool account something needed to change. I decided that making the service capable of handling multiple upstreams in parallel would be a reasonable choice.

The main user facing change for the new implementation is that configuration is now provided as a YAML document stored in the RPROXY_CONFIG envvar. The configuration should look something like:

---
routes:
  - path: /example(/|$)(.*)
    upstream: https://example.com
    template: /$2
  - path: /org(/|$)(.*)
    upstream: https://example.org
    template: /$2

This config would cause the service to expect inbound requests staring with either /example or /org which would be reverse proxied to the associated upstream server. Requests starting with any other top level path will receive a 404 response.

Bug: T414836

Merge request reports