saveIfNotExistsInBatch

Always throws — LWT cannot be mixed with regular batch statements. Named distinctly (not saveIfNotExists) for the same shadowing reason as saveInBatch/deleteInBatch: a same-named guard here would never actually be reachable, since repo.saveIfNotExists(...) would always resolve to the repository's own real, immediately-executing member instead — defeating the guard silently rather than enforcing it.