You mean kind of like this one ?

That error message is coded in user.service.js.

Yes, something like this also in the delete route:

https://github.com/genouest/genouestaccountmanager/blob/master/routes/users.js#L52
(Actually, we also need to check if the deletion workflow properly works with projects, ie the user should be removed from existing projets.

IIRC, projet membership is stored on the user, and not on the project, so we probably don't need to do anything aside from checking if the user is owner or the last member of a projet