Plane: send attitude target message implementation (for quadplanes)

Minor modification -  implementation of the send_attitude_target msg. streaming (for quadplanes). The code is analogous in its structure and functionality to the implementation in Copter

Co-Authored-By: Peter Hall <33176108+IamPete1@users.noreply.github.com>

ArduPlane/GCS_Mavlink.cpp

@@ -157,6 +157,36 @@ void GCS_MAVLINK_Plane::send_attitude() const
         omega.z);
 }
 
+void GCS_MAVLINK_Plane::send_attitude_target() 
+{
+#if HAL_QUADPLANE_ENABLED
+    // Check if the attitude target is valid for reporting
+    const uint32_t now = AP_HAL::millis();
+    if (now  - plane.quadplane.last_att_control_ms > 100) {
+        return;
+    }
+
+    const Quaternion quat  = plane.quadplane.attitude_control->get_attitude_target_quat();
+    const Vector3f& ang_vel = plane.quadplane.attitude_control->get_attitude_target_ang_vel();
+    const float throttle = plane.quadplane.attitude_control->get_throttle_in();
+
+    const float quat_out[4] {quat.q1, quat.q2, quat.q3, quat.q4};
+
+    const uint16_t typemask = 0; 
+
+    mavlink_msg_attitude_target_send(
+        chan,
+        now,                    // time since boot (ms)
+        typemask,               // Bitmask that tells the system what control dimensions should be ignored by the vehicle
+        quat_out,               // Target attitude quaternion [w, x, y, z] order, zero-rotation is [1, 0, 0, 0], unit-length
+        ang_vel.x,              // bodyframe target roll rate (rad/s)
+        ang_vel.y,              // bodyframe target pitch rate (rad/s)
+        ang_vel.z,              // bodyframe yaw rate (rad/s)
+        throttle);              // Collective thrust, normalized to 0 .. 1
+
+#endif // HAL_QUADPLANE_ENABLED 
+}
+
 void GCS_MAVLINK_Plane::send_aoa_ssa()
 {
     AP_AHRS &ahrs = AP::ahrs();

ArduPlane/GCS_Mavlink.h

@@ -32,6 +32,7 @@ protected:
 
     void send_aoa_ssa();
     void send_attitude() const override;
+    void send_attitude_target() override;
     void send_wind() const;
 
     bool persist_streamrates() const override { return true; }