Test coverage changes tracking

[yruslan]

Background [Optional]

I'm wondering if it would be possible to track test coverage changes?

The current test coverage level may be low, but we can eventually improve if new PRs are not decreasing the number.

Sorry this issue exists. But it is solely because I didn't notice that scoverage does not track test coverage level for Scala 2.13, and I let the coverage level decrease quite a bit.

Question

I'm not sure if this can me achieved with the reasonable amount of effort. But if we can add a GitHub action check that fails if a new PR decreases test coverage level, then it would encourage gradually adding test coverage to areas not very well covered now.