ci(tests): skip test cases before release

[Tomas2D]

When adding a new feature, we often generate schemas against the dev environment that cannot be used in CI. For such reason, we would like to introduce a new Pytest mark (something like @pytest.mark.not_released_yet), which would indicate that the given test should be skipped when run in the pipeline (but they should run locally - we will probably introduce some ENV for that).

When we run the release script (like poe script - see #283), those Pytest marks should be removed.