Static typing for Message, Services, and Actions

[InvincibleRMC]

trafficstars

Adds static typing to generated messages. Closes #157.

[InvincibleRMC]

Still need to fix a circular import issue.

[InvincibleRMC]

Running mypy complains about the type change within @property this doesn't effect the end user and is fine for now until #mypy300 gets resolved.

[haudren-woven]

Very nice! There is another working package here: https://github.com/rospypi/rosidl_generator_mypy

I hope this can be merged and replace the above :pray: Thank you for working on type annotations.

[InvincibleRMC]

Very nice! There is another working package here: https://github.com/rospypi/rosidl_generator_mypy

I hope this can be merged and replace the above 🙏 Thank you for working on type annotations.

If your solutions works and gets merged in I will gladly close this pr.

[haudren-woven]

Actually our solution is meant as a placeholder which you can use in your own workspace without modifying rosidl_generator_py. Last time we tried to PR this in, the maintainers did not seem to have much interest in merging it, but I'm supportive to merge your solution in: I'd rather focus our contributions on a core package such that it can benefit the larger community. From my cursory look, they look rather equivalent so let's go with it :+1: