Fix deprecated subscription callbacks in tutorials

[aprotyas]

Namely, the void (shared_ptr<MsgT>) subscription callback has
been deprecated (see ros2/rclcpp#1713).

As such, snippets using that signature have been updated with the
void (shared_ptr<const MsgT>) subscription callback.

Signed-off-by: Abrar Rahman Protyasha aprotyas@u.rochester.edu

[aprotyas]

FYI, I believe void (const MsgT&) is the best signature for "read-only" callbacks (see ros2/rclcpp#1598 (comment)), but was not sure if that's too disruptive a change in these snippets.

[aprotyas]

Also committed a couple of changes that were for a different deprecation in rosbag2_cpp::writer_interfaces::Writer (see ros2/rosbag2#866).

[clalancette]

All right, I added the fixes that make it work for me on Rolling, and I've also rebased this on top of #2095 . This looks good to me now, thanks for the update @aprotyas !

[jdlangs]

I would have thought there should be a clear preference to update things to the const & signatures here to make the documentation default simpler instead of more verbose. @aprotyas was there any specific reason you thought it might be "too disruptive"?

[aprotyas]

I would have thought there should be a clear preference to update things to the const & signatures here to make the documentation default simpler instead of more verbose. @aprotyas was there any specific reason you thought it might be "too disruptive"?

You're right. Not sure why I didn't just update to const & signatures - I reckon because I made similar changes in ros2/rclcpp#1713. I should probably also update those signatures.

Except for the rosbag tutorial, where we want to be using a shared pointer to rclcpp::SerializedMessage callback, I've updated the other read-only subscription callbacks to reflect the preferred signature (#2297).