Top-level HTTP router.

/health is unsigned liveness and /ready unsigned readiness — the first says the VM is up, the second says this node should be sent new work (see AudioProxy.Readiness, and docs/scaling.md for how to wire them). Everything else in the signed URL space — the render endpoint and /info, which share a route — is dispatched to a pipeline that verifies the signature before any other processing; an unsigned or badly-signed request is a 401 from there, and anything that matches no route at all is the JSON 404 below. /metrics is deliberately not here — it has a listener of its own (AudioProxy.Metrics.Router), and the route below says so with a 404 rather than letting it fall through to the signed one.

The signed route binds :sig and rest for dispatch only. Neither binding is read downstream: the signature covers the raw request path, which AudioProxy.Plugs.VerifySignature re-splits from conn.request_path — route bindings are percent-decoded and re-segmented, so they can never reproduce the signed bytes.

What the router owes the log

:endpoint_class names the route in the log line and is what filters /health down to debug (AudioProxy.LogHandler). It is assigned here rather than in the pipeline because a 401 halts before any pipeline plug could say what the request was asking for — which is also why the signed route assigns :render rather than the truth: only AudioProxy.Plugs.ParseOptions can tell a render from an info request, and it re-assigns :info once it has. Plug.RequestId runs ahead of matching, so every line a request produces — its own and its render's — carries the same id, and the client gets it back in x-request-id.

AudioProxy.Plugs.Cors runs ahead of matching too, and for a related reason: it registers a before-send callback that every route below shares, including the 404 and the 401 that never reach a route at all. It is also where OPTIONS stops being a 404 — but only when AP_ALLOW_ORIGIN is set, which is why the match _ clause below still owns the method for every deployment that has not enabled CORS.