chore: import upstream snapshot with attribution

apps/webapp/app/metrics.server.ts

@@ -0,0 +1,22 @@
+import type { OpenMetricsContentType } from "prom-client";
+import { Registry, collectDefaultMetrics, register } from "prom-client";
+import { singleton } from "./utils/singleton";
+import { env } from "./env.server";
+
+export const metricsRegister = singleton("metricsRegister", initializeMetricsRegister);
+
+export type MetricsRegister = Registry<OpenMetricsContentType>;
+
+function initializeMetricsRegister(): MetricsRegister {
+  const registry = new Registry<OpenMetricsContentType>();
+
+  register.setDefaultLabels({
+    serviceName: env.SERVICE_NAME,
+  });
+
+  registry.setContentType("application/openmetrics-text; version=1.0.0; charset=utf-8");
+
+  collectDefaultMetrics({ register: registry });
+
+  return registry;
+}