fix: move implementation to "internal" package

internal/handler/middleware/wrapper.go

@@ -0,0 +1,14 @@
+package middleware
+
+import "net/http"
+
+// Chain list of handlers together.
+func Wrapper(next http.Handler, handlers ...func(http.Handler) http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		lastHandler := next
+		for _, handler := range handlers {
+			lastHandler = handler(lastHandler)
+		}
+		lastHandler.ServeHTTP(w, r)
+	})
+}