test: add reverse proxy deployment check

internal/perfcheck/main.go

@@ -181,6 +181,16 @@ func serve(adapter string, tlsEnabled bool) error {
 	application.GET("/health", func(c *omni.Context) error {
 		return c.OK(map[string]string{"status": "ok"})
 	})
+	application.GET("/slow", func(c *omni.Context) error {
+		timer := time.NewTimer(2 * time.Second)
+		defer timer.Stop()
+		select {
+		case <-timer.C:
+			return c.OK(map[string]string{"status": "slow"})
+		case <-c.Context().Done():
+			return c.Context().Err()
+		}
+	})
 	done := make(chan error, 1)
 	var shutdown func(context.Context) error
 	switch adapter {