Add Support for Nested (Parental) Groups in Group Memberships

Implement support for nested or parental groups within the group management system. This allows users assigned to a child group to automatically inherit membership of all parent groups. The feature should also integrate with external identity providers such as Entra (Azure AD), where nested group structures are commonly used.

This functionality is essential for managing access via ACLs based on hierarchical group membership without manually duplicating users across multiple groups.

Acceptance Criteria:

- When a user is a member of a child group, they are implicitly treated as a member of all ancestor (parent) groups.
- Group membership resolution accounts for nested groups both during synchronization from external providers (e.g., Entra) and during login/session validation.