flight tasks: move weather vane yaw handler from Altitude to Position task

src/lib/FlightTasks/tasks/ManualPosition/FlightTaskManualPosition.cpp

@@ -147,6 +147,13 @@ void FlightTaskManualPosition::_updateXYlock()
 void FlightTaskManualPosition::_updateSetpoints()
 {
 	FlightTaskManualAltitude::_updateSetpoints(); // needed to get yaw and setpoints in z-direction
+
+	// check if an external yaw handler is active and if yes, let it update the yaw setpoints
+	if (_weathervane_yaw_handler != nullptr && _weathervane_yaw_handler->is_active()) {
+		_yaw_setpoint = NAN;
+		_yawspeed_setpoint += _weathervane_yaw_handler->get_weathervane_yawrate();
+	}
+
 	_thrust_setpoint.setAll(NAN); // don't require any thrust setpoints
 	_updateXYlock(); // check for position lock
 }

src/lib/FlightTasks/tasks/ManualPosition/FlightTaskManualPosition.hpp

@@ -51,6 +51,11 @@ public:
 	bool activate() override;
 	bool updateInitialize() override;
 
+	/**
+	 * Sets an external yaw handler which can be used to implement a different yaw control strategy.
+	 */
+	void setYawHandler(WeatherVane *yaw_handler) override { _weathervane_yaw_handler = yaw_handler; }
+
 protected:
 	void _updateXYlock(); /**< applies position lock based on stick and velocity */
 	void _updateSetpoints() override;
@@ -65,4 +70,8 @@ protected:
 private:
 	float _velocity_scale{0.0f}; //scales the stick input to velocity
 	uint8_t _reset_counter{0}; /**< counter for estimator resets in xy-direction */
+
+	WeatherVane *_weathervane_yaw_handler =
+		nullptr;	/**< external weathervane library, used to implement a yaw control law that turns the vehicle nose into the wind */
+
 };