[FIX] base: prevent deletion of group linked to settings field

before this commit, if tries to delete a user group
which is linked with a field in settings, ie, via
implied_groups in res.config.settings or used in the
field group, there is no restriction and user group
will get deleted.

and then if user tries to access any settings page
the traceback will be shown to user.

after this commit, on deleting any user group
which is linked with a field in res.config.settings,
a validation message will be shown to the user that
the group cannot be deleted as it is linked with
a settings field.

closes odoo/odoo#123905

X-original-commit: ef3dfd02012e16c88789137f5eb0ec49b22f4df8
Signed-off-by: Xavier Morel (xmo) <xmo@odoo.com>

odoo/addons/base/i18n/base.pot

@@ -31065,6 +31065,12 @@ msgstr ""
 
 #. module: base
 #. odoo-python
+#: code:addons/base/models/res_users.py:0
+#, python-format
+msgid "You cannot delete a group linked with a settings field."
+msgstr ""
+
+#. module: base
 #: code:addons/base/models/res_partner.py:0
 #, python-format
 msgid ""

odoo/addons/base/models/res_users.py

@@ -153,6 +153,13 @@ class Groups(models.Model):
     def _check_one_user_type(self):
         self.users._check_one_user_type()
 
+    @api.ondelete(at_uninstall=False)
+    def _unlink_except_settings_group(self):
+        classified = self.env['res.config.settings']._get_classified_fields()
+        for _name, _groups, implied_group in classified['group']:
+            if implied_group.id in self.ids:
+                raise ValidationError(_('You cannot delete a group linked with a settings field.'))
+
     @api.depends('category_id.name', 'name')
     def _compute_full_name(self):
         # Important: value must be stored in environment of group, not group1!