Install dependencies via poetry and specify authors

• Dependency install via poetry
  • This aims to make the report creation more reproducible in order to rely on pinned dependency versions
  • Dependencies are not secretly specified in .gitlab-ci.yml but are explicitly stated where people would expect them.
• Add a reuse stage to .gitlab-ci.yml

Follow-up of !152 (merged) to switch install to Poetry and specify authors via pyproject.toml. !152 (merged) needs to be merged first.