Add camera sensor frame_id variable

[MarqRazz]

This adds the ability to specify the frame_id that is used when publishing images from the camera sensor. This feature request was noted in CameraSensors.cc and will help close issue 175 in ign-sensors.

This is my first PR here so I'm sure there are a few things I need to clean up. Below are a few questions I had.

• I am targeting this against Fortress with ROS Rolling. Is sdf12 the correct branch to base this off of?
• What do I need to do to update the webpage documentation for the camera sensor?
• I also have a PR ready that modifies CameraSensor.cc to utilize this variable. I will get that pushed up after I get some feedback here and know that I'm on the correct route to getting this feature added.

I named the variable optical_frame_id because it is associated with the camera_info message which normally contains the header value with the frame_id that is set to the optical frame name of the sensor.

I am also looking to add a variable point_cloud_frame_id so that I can set the frame_id name that the point cloud is published from (in the current RGBD implementation this value is set to the Name() of the node which does not seem correct or helpful to consumers of the data). I decided to not include that change here until I get some feedback from the maintainers. If you feel that this is in scope of this PR I can add it.

🎉 New feature

Summary

This adds the sdf parameter <optical_frame_id> to the Camera sensor. This allows the user to specify the frame_id that is returned in the message published from CameraSensor.cc.

Test it

This PR only add the ability to specify the tag <optical_frame_id> which is not required. Follow up PR's will be made against ign-sensors to utilize it.

Checklist

• Signed all commits for DCO
• Added tests
• Added example and/or tutorial
• Updated documentation (as needed)
• Updated migration guide (as needed)
• 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.

[scpeters]

Thanks for your contribution. In order to add support for new fields to SDFormat, the files in the sdf/1.X folders need to be updated in addition to the c++ DOM files. See #651 for an example that added an <enable_orientation/> field to the <imu/>. Let me know if you have any questions.

[chapulina]

@MarqRazz , are you still interested in moving forward with this PR? Did you give any thought to @scpeters 's comment?

[MarqRazz]

I am so sorry for completely dropping the ball here. I had the best intentions to get this across the finish line at the beginning of the year but this keeps falling off my schedule. According to the issue I created this work is partly complete. I will not have time to work on this in the near future so please feel free to close the PR and I will open a new one if I get time to complete it.