Create worker-skeleton

[Veldhoen]

Bare essentials for a Dane worker (may deserve its own repo in the end?)

• [x] worker.py
• [x] models.py
• [x] base_util.py
• [x] io_util.py
• [x] main_data_processor.py with some dummy processing
• [x] pyproject.toml
• [x] config

- [ ] dockerfile

And most of all: check that the setup works with dummy processing locally & in container (& with S3?)

[Veldhoen]

Move containerization to a separate issue

[Veldhoen]

Todo: adding docstrings - new issue