Rewrite of old rosidl tutorial

[maryaB-osr]

The old rosidl tutorial had some concepts in it that I didn't cover in my new "simple" interface tutorial (because it's already too long) so instead of deleting the old one, I rewrote it and removed all the repeated information between the two.

The code works now but I'm not sure if it's "right".

This bit of code in the original:

get_default_rmw_implementation(rmw_implementation)
find_package("${rmw_implementation}" REQUIRED)
get_rmw_typesupport(typesupport_impls "${rmw_implementation}" LANGUAGE "cpp")

foreach(typesupport_impl ${typesupport_impls})
  rosidl_target_interfaces(publish_address_book
    ${PROJECT_NAME} ${typesupport_impl}
  )
endforeach()

works, but I replaced it with this because it's much shorter:

  rosidl_target_interfaces(publish_address_book
    ${PROJECT_NAME} "rosidl_typesupport_cpp")

Is there a different situation for each of these? If that longer block is meant for a specific purpose, I'd like to include that in the tutorial.

fixes #565

[hidmic]

Overall LGTM but for a few details.

[clalancette]

Overall, I like what you've done here. I think this is a good article to have.

One thing that I think we should change is the name of the article. "More-Interfaces" isn't very descriptive. I'd go with something like "Single-Package-Define-and-Use-Interface", but anything along those lines is OK with me. I've got a few other small things inline, though I didn't do a full review this time. Once things are renamed I can do another look over.

[clalancette]

Overall, I like the direction this one is going in. I've done a more thorough review now and have left a few more comments for you to think about.

[clalancette]

Hm, didn't we decide not to point to the tutorials repository as it doesn't really work right now?

[maryaB-osr]

Yeah it looks bad :/ but that's the msg we're using for the following example to show that you can use existing interfaces to define new ones.

Aside from having them create Contact.msg themselves in another package (meaning they'll have to go create another package just for that), or rewriting the example to use an existing msg from some up-to-date package in the ecosystem (which would also make the tutorial longer because a completely new publisher would have to be written to accommodate a different msg), I don't see a way around linking to Contact.

I rewrote the sentence to take the focus off the rosidl_tutorials package at least:

For example, let's use Contact.msg <https://github.com/ros2/tutorials/blob/rosidl_tutorials/rosidl_tutorials/rosidl_tutorials_msgs/msg/Contact.msg>_, which belongs to an existing ROS 2 package.

[clalancette]

Fair enough. I don't love it, but since that is the point of that section, so be it.