FOsterfeld

split dimension is a batch dimension ## Due Diligence - General: - [ ] **base branch** must be `main` for new features, latest release branch (e.g. `release/1.3.x`) for bug fixes...

## Due Diligence - General: - [x] **title** of the PR is suitable to appear in the [Release Notes](https://github.com/helmholtz-analytics/heat/releases/latest) - Implementation: - [x] unit tests: all split configurations tested -...