Include downloading of raw files in the integration test

[jankrepl]

🚀 Feature

Recently, we implemented bbs_database download for multiple different sources. It might be a good idea to extend our integration test to actually use this download (rather than using data committed to the repo).

Motivation

• We make sure that our ETL pipeline works end to end
• Possibility to detect upstream changes on the source servers

[Stannislav]

We might consider only running this sparsely, e.g. only on merges to master or according to some schedule?