fix: move implementation to "internal" package

internal/handler/middleware/cache_control.go

@@ -0,0 +1,18 @@
+package middleware
+
+import (
+	"net/http"
+	"strings"
+)
+
+func CacheControl(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		shouldCache := strings.HasPrefix(r.URL.Path, "/static")
+
+		if !shouldCache {
+			w.Header().Set("Cache-Control", "no-cache, no-store, must-revalidate")
+		}
+
+		next.ServeHTTP(w, r)
+	})
+}