Use the same terminology in base and in manager
Today I found out that "None" in the manager, is "Null" in db for "passwordDB" (this is an example).
We document a "Null" auth : https://lemonldap-ng.org/documentation/latest/authnull.html
I think I would be a good idea to use "Null" inside the manager instead of "None"
I will try to provide a PR later, let me know what to you think.