Prevent local account takeover
    
    It was found that if an account was created with a name corresponding to
    an account local to a system, such as 'root', was created via IPA, such
    account could access any enrolled machine with that account, and the local
    system privileges. This also bypass the absence of explicit HBAC rules.
    
    root principal alias
    -------------------
    
    The principal "root@REALM" is now a Kerberos principal alias for
    "admin". This prevent user with "User Administrator" role or
    "System: Add User" privilege to create an account with "root" principal
    name.
    
    Modified user permissions
    -------------------------
    
    Several user permissions no longer apply to admin users and filter on
    posixaccount object class. This prevents user managers from modifying admin
    acounts.
    
    - System: Manage User Certificates
    - System: Manage User Principals
    - System: Manage User SSH Public Keys
    - System: Modify Users
    - System: Remove Users
    - System: Unlock user
    
    ``System: Unlock User`` is restricted because the permission also allow a
    user manager to lock an admin account. ``System: Modify Users`` is restricted
    to prevent user managers from changing login shell or notification channels
    (mail, mobile) of admin accounts.
    
    New user permission
    -------------------
    
    - System: Change Admin User password
    
    The new permission allows manipulation of admin user password fields. By
    default only the ``PassSync Service`` privilege is allowed to modify
    admin user password fields.
    
    Modified group permissions
    --------------------------
    
    Group permissions are now restricted as well. Group admins can no longer
    modify the admins group and are limited to groups with object class
    ``ipausergroup``.
    
    - System: Modify Groups
    - System: Remove Groups
    
    The permission ``System: Modify Group Membership`` was already limited.
    
    Notes
    -----
    
    Admin users are mostly unaffected by the new restrictions, except for
    the fact that admins can no longer change krbPrincipalAlias of another
    admin or manipulate password fields directly. Commands like ``ipa passwd
    otheradmin`` still work, though. The ACI ``Admin can manage any entry``
    allows admins to modify other entries and most attributes.
    
    Managed permissions don't install ``obj.permission_filter_objectclasses``
    when ``ipapermtargetfilter`` is set. Group and user objects now have a
    ``permission_filter_objectclasses_string`` attribute that is used
    by new target filters.
    
    Misc changes
    ------------
    
    Also add new exception AlreadyContainsValueError. BaseLDAPAddAttribute
    was raising a generic base class for LDAP execution errors.
    
    Fixes: https://pagure.io/freeipa/issue/8326
    Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1810160
    Signed-off-by: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>
    Reviewed-By: Florence Blanc-Renaud <flo@redhat.com>