PollingObserver - make init() private

src/utils.hh

@@ -130,12 +130,6 @@ namespace Heck {
         PollingObserver(PollingObserver&&) = delete;
         PollingObserver& operator=(PollingObserver&&) = delete;
 
-        void init(FetchCallback fetch_cb, DeliverCallback deliver_cb)
-        {
-            set_fetch_callback(fetch_cb);
-            set_deliver_callback(deliver_cb);
-        }
-
         void set_fetch_callback(FetchCallback cb)
         {
             fetch_cb_ = cb;
@@ -169,6 +163,12 @@ namespace Heck {
         }
 
     private:
+        void init(FetchCallback fetch_cb, DeliverCallback deliver_cb)
+        {
+            set_fetch_callback(fetch_cb);
+            set_deliver_callback(deliver_cb);
+        }
+
         T val_current_{};
         FetchCallback fetch_cb_{};
         DeliverCallback deliver_cb_{};