[IMP] base: Synchronize template user new groups with existing users

Purpose
=======

The template user groups are applied to new users, but this is not the
case for existing users.

To harmonize the flow, the added groups to the default user template are
synchronized with the existing users.

closes odoo/odoo#101086

X-original-commit: aefb05eb497a8a16a9359432f41024c09552ed70
Related: odoo/enterprise#31759
Signed-off-by: Yannick Tivisse (yti) <yti@odoo.com>

odoo/addons/base/models/res_users.py

@@ -593,7 +593,20 @@ class Users(models.Model):
                 # safe fields only, so we write as super-user to bypass access rights
                 self = self.sudo().with_context(binary_field_real_user=self.env.user)
 
+        if 'groups_id' in values:
+            default_user = self.env.ref('base.default_user', raise_if_not_found=False)
+            if default_user and default_user in self:
+                old_groups = default_user.groups_id
+
         res = super(Users, self).write(values)
+
+        if 'groups_id' in values and default_user and default_user in self:
+            # Sync added groups on default user template to existing users
+            added_groups = default_user.groups_id - old_groups
+            if added_groups:
+                internal_users = self.env.ref('base.group_user').users - default_user
+                internal_users.write({'groups_id': [Command.link(gid) for gid in added_groups.ids]})
+
         if 'company_id' in values:
             for user in self:
                 # if partner is global we keep it that way