Automatic checking of row counts for update* when only <= 1 row is expected to be affected

Feature description

Safe/sanity checked usage of update methods currently requires code like this:

var rowCount = repository.updateFooById(id);
if (rowCount != 1) {
    throw IllegalStateException("Update of FOO by id %s should have affected 1 row but affected %d".formatted(id, rowCount));
} 

If you don't check it's possible an update silently touches more or less data than you expected, which isn't ideal.

It'd be good if Micronaut Data could do this sort of check for you. I'm thinking something like @MustUpdateOne and @MaybeUpdatesOne annotations on update methods. The former would ensure rowcount == 1, the latter that it's <= 1 and I don't think there's much point in having more flexibility than that.

Start by reviewing the update* repository methods and the existing row-count handling in Micronaut Data. Define how the proposed @MustUpdateOne and @MaybeUpdatesOne annotations should behave, then verify that updates enforce exactly one row or no more than one row as specified.