New Apply Link Wrench system

[chapulina]

🎉 New feature

• Related to Mouse interaction with simulated models #306
• Requires
  • Add entity wrench message gz-msgs#274
• Builds on top of
  • Add Model::CanonicalLink getter #1594
  • Helper function to get an entity from an entity message #1595

Summary

I needed a convenient way of applying forces to models without a plugin, so I thought I'd add a system that exposes a topic for applying wrenches to links.

The idea is similar to Gazebo classic's ~/scoped/link/name/wrench topic, but here there's a single topic for the entire world, and the exact entity is defined in the message. This way, we don't pollute the topic space, allow different ways of choosing entities (by ID, by type, etc), and don't need to instantiate the plugin for each entity.

I needed to add a few different things to implement this plugin. I'll break this into smaller PRs for each functionality, adding tests as needed.

Test it

Try the example world:

ign gazebo src/ign-gazebo/examples/worlds/apply_link_wrench.sdf

With example commands, i.e.

ign topic -t "/world/apply_link_wrench/wrench" -m ignition.msgs.EntityWrench  -p "entity: {name: 'box::link', type: LINK}, wrench: {force: {x: -1000, z: 10000}, torque: {y: -1000}}"

Checklist

• Signed all commits for DCO
• Added tests
• Added example and/or tutorial
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

🔸🔸🔸🔸🔸🔸🔸🔸🔸🔸🔸🔸🔸🔸🔸🔸🔸🔸🔸🔸🔸🔸🔸🔸🔸🔸🔸🔸🔸🔸🔸🔸🔸🔸🔸🔸🔸

[quarkytale]

Works for me!
(Nit the apply wrench on box command in the description has "type" missing, fixed it)