When running open world, we can add, but not remove constellations

[CerielJacobs]

... but we should be able to remove them as well.

[jmaassen]

Removing constellations leads to a big can of worms with lost jobs, unroutable events, etc. That's why I never dared to implement it ;-)

[CerielJacobs]

True. It sounds very tricky indeed, especially with event routing. It is probably doable to stop executors from stealing jobs, and waiting until all activities are done (although that, by itself, might cause deadlocks...).