add test coverage reporting in CI

[serhalp]

No blocking coverage % thresholds on PRs or anything like that. Just surfacing coverage reports on PRs/commits for convenient reference.

What do the cool kids use these days? Codecov?

[LeonhardHoffmann]

Hey @serhalp, would like to take this one as my first contribution on your project. Do I understand it correctly that you want to have the % of code coverage automaticly attached to the pr message?

Like I open a pr, write my message and when i send it the % gets attached?

[serhalp]

Hey @LeonhardHoffmann, thanks for contributing!

I think just the % alone is not very valuable. Ideally what we want is the full coverage report.

Come to think of it, I think this might be (depending on how we choose to go about it) something only an admin can set up. Since we're already reporting coverage (I think) from all our tests, I think @danielroe would just need to install the GitHub Codecov app and add the CI workflow with the token.

Don't hesitate to grab another issue you find interesting though!