We are currently keeping track of upgrades step by their type, the indices they upgrade and the `stepNumber`. Unfortunately, sometimes the number of steps in an upgrade are data dependent, which results in a different number of steps depending on the state of data when the upgrade was started. The upgrade stepNumber is therefore not a reliable way of tracking upgrade progress in the context of a resumed upgrade.
For example: in the current upgrade, we create a list of upgrade steps that reindex instance data to new instance indices, and then later delete the old instance index. This means that if an upgrade is resumed after the old instance index is already deleted, there are no more definition keys to create new instance indices for, which means there will be a different number of upgrade steps.
- Upgrade stepnumber is no longer used as identification of which upgrade steps have already run