WIP: The refactoring

This is just a WIP MR to aggregate results/issues of the upcoming refactoring. If the refactoring takes longer than expected we at least still have a working master branch for intermediate releases.

• #493 (closed)
• #567 (closed)
• #291 (closed)
• #566 (closed)
• #688 (closed)
• #689 (closed)

(Optional)

• #564 (closed) (requires #291 (closed))