[Experiment] Enable CodeCov

[wilzbach]

In theory that should be all that's needed to get CodeCov reports on the CI status report.

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@b37fcf5). Click here to learn what that means.
The diff coverage is n/a.

@@           Coverage Diff            @@
##             master    #144   +/-   ##
========================================
  Coverage          ?   7.13%           
========================================
  Files             ?       7           
  Lines             ?    4524           
  Branches          ?       0           
========================================
  Hits              ?     323           
  Misses            ?    4201           
  Partials          ?       0

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[wilzbach]

hmm it seems that the .codecov.yml file is only taken into account when its part of the target branch.

[keywan-ghadami-oxid]

Hi, yes it seams it is needed on the target branch too, to be able to compare results. But also it seams to work on this branch/mergerequest.

[wilzbach]

I am taking the liberty as this has nothing to do with the codebase and I am giving this experiment a shot. If CodeCov turns out to be unstable, we can always disable this.