Backward compatibility with humble

Author: devis12

behaviortree_ros2/include/behaviortree_ros2/bt_service_node.hpp

@@ -216,8 +216,12 @@ inline RosServiceNode<T>::ServiceClientInstance::ServiceClientInstance(
       node->create_callback_group(rclcpp::CallbackGroupType::MutuallyExclusive, false);
   callback_executor.add_callback_group(callback_group, node->get_node_base_interface());
 
-  service_client = node->create_client<T>(service_name, rclcpp::QoS(rclcpp::ServicesQoS()),
-                                          callback_group);
+  #if RCLCPP_VERSION_MAJOR >= 21  // Iron, Jazzy and later
+    service_client = node->create_client<T>(service_name, rclcpp::QoS(rclcpp::ServicesQoS()),
+                                            callback_group);
+  #else  // Humble
+    service_client = node->create_client<T>(service_name, rmw_qos_profile_services_default, callback_group);
+  #endif
 }
 
 template <class T>