However there is a usecase where it would be useful to change a users username
for example if using SSO the system expects the username to be an email address or a upn (user principal name)
if the users upn changes they will not be able to use the cloud again unless they are setup with a new account and have all their shares and files moved over which in some cases is a big undertaking.
I propose to make these tasks easier for people in the future that the users username is not used as a key within database tables and instead a user id field is introduced to be used as a key instead.
If username is set, it cannot be changed anymore. If deleted and created new (same username) the user cannot access the same account as before, because the user-id behind the username is unique.
It is the same as with Windows user accounts, where a UUID is behind the username and a new one will be given after deletion and recreating the user.
The user/You only can modify the display name of a user.