User Identity Migration: Transition from Username to UserID

[hbenali]

Is your feature request related to a problem? Please describe.
A user is identified by a username generated from their full name (most of the time). Their full name would be changed for such needs (name Change, manual username change, etc...)
Describe the solution you'd like
Modify the user identity system by replacing the username as the unique identifier with an ID (e.g., UUID or incremental ID) to serve as the internal system user ID. The username and email will remain as the primary inputs for authentication.
This change will significantly affect various authentication services and protocols (e.g., AD (LDAP), SAML, OpenID), and product permissions change necessitating a thorough impact analysis of these modifications.

Thanks