Update Metric.scala

server/core/src/main/scala/sttp/tapir/server/metrics/Metric.scala

@@ -64,3 +64,22 @@ object MetricLabels {
     )
   )
 }
+
+object OTELMetricLabels {
+
+  /** Labels request by path and http.request.method, response by http.response.status_code */
+  lazy val Default: MetricLabels = MetricLabels(
+    forRequest = List(
+      "http.request.method" -> { case (_, req) => req.method.method },
+      "path" -> { case (ep, _) => ep.showPathTemplate(showQueryParam = None) }
+    ),
+    forResponse = List(
+      "http.response.status_code" -> {
+        // OpenTelemetry-compliant
+        case Right(r) => r.code.code.toString
+        // Default to 500 for exceptions
+        case Left(_) => "500"
+      }
+    )
+  )
+}