Backfill test that user can't create models without permission
prevent two CCs from updating the same row at once

[#47767303]
fix apps becoming unstoppable after many concurrent updates

Previously stop events were registered based on the most recent start
event by timestamp. With many concurrent start/top requests, it's
possible for start events to occur in the same instant as determined by
the database, thus the stop event would potentially be registered for a
start event that already has a corresponding stop event. This would make
the stop request fail because of uniqueness constraints (by kind and
run_id).

[finishes #47767303]
fix stopping an app that already has a stop event

this is an edge case, but would leave the user being charged for an app
that they cannot stop or delete

[finishes #47767303]