Changing indices in property definitions can sometimes break things #178
Description
The main problem is that there is no migration guidance and migration needs to be taken into account for things like this.
Currently when setting a property to be indexed on an existing model but there are already instances that don't have this index saved, the method for deciding whether to remove old indices is broken.
What exactly is going wrong is still slightly unclear. There might not be a way to fix this without writing migrations.