[traffic] API to reconfigure a running HttpTrafficSource

Signed-off-by: mvglasow <michael -at- vonglasow.com>

traffxml/traff_source.hpp

@@ -441,6 +441,15 @@ public:
    */
   static void Create(TraffSourceManager & manager, std::string const & url);
 
+  /**
+   * @brief Prepares the HTTP traffic source for unloading.
+   *
+   * If there is still an active subscription, it unsubscribes, but without processing the result
+   * received from the service. Otherwise, teardown is a no-op.
+   */
+  // TODO move this to the parent class and override it here?
+  void Close();
+
   /**
    * @brief Subscribes to a traffic service.
    *