Create a better way to run integration tests only on CI

[paullatzelsperger]

currently we have integration tests that are annotated with @EnabledIfEnvironmentVariable(named = "CI", matches = "true") and then we need to evaluate the CI env var again in the @BeforeAll because that one still would get called.

@BeforeAll
public static void setup() {
     // this is necessary because the @EnabledIf... annotation does not prevent @BeforeAll to be called
     var isCi = propOrEnv("CI", "false");
     if(!Boolean.parseBoolean(isCi)) return;
}

Maybe this can be achieved with custom composed annotations (cf. Junit Docs)