Ensure that only 1 model run can be requested during setup at any one time. This is to ensure no potential conflicts caused by the same disease group's data being updated in two different transactions.
Batching: the minimum date is now the minimum occurrence date. This allows a reattempt at batching if it failed. There is no danger of the same occurrence being batched twice because only occurrences with status AWAITING_BATCHING are batched.