Mirrors the nginx allowlist (spec section D) so make dev-web matches prod: when OPENCONCHO_UPSTREAM_ALLOWLIST is set, non-matching upstreams get 403 + X-Honcho-Proxy-Reject; unset stays open.
Mirrors the nginx allowlist (spec section D) so make dev-web matches prod: when OPENCONCHO_UPSTREAM_ALLOWLIST is set, non-matching upstreams get 403 + X-Honcho-Proxy-Reject; unset stays open.