Add deprecation messages to all messages now in example_interfaces

[tfoote]

Followup to #89

[hidmic]

I wonder about the rationale behind deprecating what's in std_msgs and moving it to example_msgs. It's been like this in ROS 1 for over a decade, why the change?

[hidmic]

@tfoote consider

Suggested change

	# It is deprecated as of Foxy, it is recommended to create your own
	# It is deprecated as of Foxy.
	# It is recommended that you create your own

same elsewhere.

[tfoote]

Thanks that reads better, updated.

[tfoote]

It's been in ROS 1 that we generally recommend against using almost any message in std_msgs except Header for a long time for stability.
From the Overview: http://wiki.ros.org/std_msgs

However, these types do not convey semantic meaning about their contents: every message simply has a field called "data". Therefore, while the messages in this package can be useful for quick prototyping, they are NOT intended for "long-term" usage. For ease of documentation and collaboration, we recommend that existing messages be used, or new messages created, that provide meaningful field name(s).

Note that this package also contains the "MultiArray" types, which can be useful for storing sensor data. However, the same caveat applies: it's usually "better" (in the sense of making the code easier to understand, etc.) when developers use or create non-generic message types (see discussion in this thread for more detail).

However from the naming it leads to a lot of confusion.(For example) And we want to take the opportunity in ROS 2 to avoid that ambiguity. The earlier we do it in this cycle the easier and less disruption it will cause.

[jacobperron]

LGTM. Though their usage has been discouraged for a long time now, it might be worth highlighting that we have "officially" deprecated them in the Foxy release notes.

[jacobperron]

I guess we shouldn't have run CI for this change since it caused a test failure downstream: https://ci.ros2.org/view/nightly/job/nightly_linux_release/1548/testReport/ros2interface.src.ros2.ros2cli.ros2interface.test/test_cli/test_cli/

See a fix in ros2/ros2cli#516

[ros-discourse]

This pull request has been mentioned on ROS Discourse. There might be relevant details there:

https://discourse.ros.org/t/soss-a-whole-new-approach-to-your-ros-1-ros-2-bridge/17040/18

[ros-discourse]

This pull request has been mentioned on ROS Discourse. There might be relevant details there:

https://discourse.ros.org/t/discussion-standardizing-ros-interfaces/33693/1