A collection minor fixes + hotfix (error 500 on production in some circumstances)

- Improve users test names to more human readable ones.
- Normalize some test filenames.
- Fix wrong handling of moveTo parameter on role destroy. 
- Fix unhandled internal server error (in very strange circumstances) on destroy role.

(we have received several notifications about this error, and the last commit should fix this, obvioulsy with test that reproduces the error included ;))