Add CodeCov on the repository

[Hugo Herter]

First, we need to run the tests outside of Docker and with coverage.

Then in the GitHub Actions:

After tests run, this will upload the coverage report to Codecov:

  uses: codecov/codecov-action@v4.0.1
  with:
    token: ${{ secrets.CODECOV_TOKEN }}
    slug: aleph-im/aleph-client

After you committed your changes and ran the repo's CI/CD pipeline. In your pull request, you should see two status checks and PR comment.

Once merged to the default branch, subsequent pull requests will have checks and report comment. Additionally, you'll find your repo coverage dashboard here.