Core: Cannot update user nickname to empty

[maximeroucher]

Subject of the issue

This is due to .values(**user_update.model_dump(exclude_none=True)), in the update user cruds, since we want the nickname to be null.

Your environment

• Any version of Hyperion
• Any operating system

Steps to reproduce

Change a user nickname, with any tools you like

Expected behaviour

The user nickname should be empty

Actual behaviour

The user nickname remains unchanged