Check whether any other record, in any entity, still has a single-field foreign key pointing
at entity.property = value - the mirror image of foreignKeyExists(), which checks the opposite
direction (that a new/updated foreign key value points at something real). Used to RESTRICT a
delete or update that would otherwise leave a dangling reference behind. Scans every record in
the database via the __RECORDS registry, the same "no index needed, just look" approach as
keyUnique()/foreignKeyExists() - correctness over speed, matching this project's overall scale.
Check whether any other record, in any entity, still has a single-field foreign key pointing at entity.property = value - the mirror image of foreignKeyExists(), which checks the opposite direction (that a new/updated foreign key value points at something real). Used to RESTRICT a delete or update that would otherwise leave a dangling reference behind. Scans every record in the database via the __RECORDS registry, the same "no index needed, just look" approach as keyUnique()/foreignKeyExists() - correctness over speed, matching this project's overall scale.