Integrate code coverage

[wolf4ood]

Describe the solution you'd like

It would be cool to integrate a coverage tool in the repository and in the PRs workflow

We should have in the main README a pointer in the current coverage status and we
integrate a tool that calculate the impact in coverage diff in PR.

Describe the solution you'd like

In upstream EDC the combination of Jacoco + Codecov it's used. Probably make sense to use the same
setup

[paullatzelsperger]

Tractus-X uses SonarCloud to evaluate coverage, and we already have Jacoco. Could be that the merged jacoco report is somehow incomplete, or doesn't get created, which should be investigated.

[paullatzelsperger]

I'll re-open this, because according to the documentation, the automatic analysis does not support Code Coverage.
We therefor have to switch back to CI-triggered analysis. I'll open another PR for that. This will, however, only enable Sonar analysis on commits in upstream, no PRs.

Since all our test jobs are spread across multiple jobs (for parallelization), we'll need to collect all the test results (upload/download artefacts), generate the aggregate report and then upload them to sonar. It's questionable whether that is worth the effort.

[paullatzelsperger]

to reiterate: we either have automatic Sonar analysis on every commit, but we'll have no coverage analysis, or we perform the analysis manually, but only on upstream commits.

Alternatively, we could introduce another tool just for coverage but that seems a bit over-the-top.