Remove default_value for required arguments

[Amronos]

🦟 Bug fix

Removes default_value for config_file and bridge_name due to them being a required argument.
Changes string and xml_string to world_string in various places to maintain consistency, make clarification, and make fixes.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
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• All tests passed (See test coverage)
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[caguero]

Thanks for the patch!

Could you fix the conflicts?

[caguero]

I also see config_file instances to be updated in:

• ros_gz_bridge/launch/ros_gz_bridge.launch
• ros_gz_bridge/launch/ros_gz_bridge.launch.py

[Amronos]

Changed xml_string to string in various places to maintain consistency and make fixes. Please review that too.

[caguero]

Changed xml_string to string in various places to maintain consistency and make fixes. Please review that too.

Naming is hard but I thought xml_string was a lightly better name than string. Maybe sdf_string is better? I don't have a strong opinion here :) . Maybe world_string?

[Amronos]

I think now there are no more changes to be made. Can this merged?