[change] Make batch import atomic

[nemesifier]

I was reviewing the batch CSV import code due to #550 and it seems to me the create operation is not atomic.

What if the import operation fails in the middle?

I believe we would end up with half users created.

I think it's better to make everything run in a transaction and if anything fails rollback.

[shwetd19]

Hey @nemesifier , I'm Shwetas, I am a final-year BTech-CSE student. I have strong experience in Java, JavaScript, and the Full-Stack. I’ve worked on open-source projects and built SaaS platforms, and I believe I can contribute effectively to this project. I would be grateful for the opportunity to be assigned to this issue.