fix: cleanly exit on shutdown (#5537)

Co-authored-by: Mm2PL <mm2pl+gh@kotmisia.pl>
Co-authored-by: Nerixyz <nerixdev@outlook.de>

src/providers/liveupdates/BasicPubSubClient.hpp

@@ -150,6 +150,15 @@ protected:
         return this->started_.load(std::memory_order_acquire);
     }
 
+    /**
+     * @brief Will be called when the clients has been requested to stop
+     *
+     * Derived classes can override this to implement their own shutdown behaviour
+     */
+    virtual void stopImpl()
+    {
+    }
+
     liveupdates::WebsocketClient &websocketClient_;
 
 private:
@@ -164,6 +173,8 @@ private:
     {
         assert(this->isStarted());
         this->started_.store(false, std::memory_order_release);
+
+        this->stopImpl();
     }
 
     liveupdates::WebsocketHandle handle_;