feat(observabillity): #115 integrate otel for metrics and traces

internal/handler/middleware/cache_control.go

@@ -3,10 +3,15 @@ package middleware
 import (
 	"net/http"
 	"strings"
+
+	"go.opentelemetry.io/otel"
 )
 
 func CacheControl(next http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		counter, _ := otel.Meter("").Int64Counter("spend.sparrow.test")
+		counter.Add(r.Context(), 1)
+
 		shouldCache := strings.HasPrefix(r.URL.Path, "/static")
 
 		if !shouldCache {