[FIX] base: Prevent user_admin deletion

Purpose
=======

Tremendous amount of support tickets (ex: 3800405) are opened because the user_admin
has been removed and is referenced everywhere, leading to tracebacks or
the impossibility to install a new application as res.group configurations
all relies on this, like:

<record id="group_helpdesk_manager" model="res.groups">
    <field name="name">Administrator</field>
    <field name="category_id" ref="base.module_category_services_helpdesk"/>
    <field name="implied_ids" eval="[(4, ref('group_helpdesk_user'))]"/>
    <field name="users" eval="[(4, ref('base.user_root')), (4, ref('base.user_admin'))]"/>
</record>

We could adapt all the occurences (severeal hundreds) to ensure robustness
but this won't prevent developer from introducing new use cases + the user
can be archived instead if we want to remove him from the pricing.

closes odoo/odoo#158885

Taskid: 3802440
X-original-commit: b55994b4c5e737aae593eb0419f96347ad90bebb
Signed-off-by: Yannick Tivisse (yti) <yti@odoo.com>

odoo/addons/base/i18n/base.pot

@@ -31914,6 +31914,15 @@ msgstr ""
 msgid "You cannot delete the %s record."
 msgstr ""
 
+#. module: base
+#. odoo-python
+#: code:addons/base/models/res_users.py:0
+#, python-format
+msgid ""
+"You cannot delete the admin user because it is utilized in various places "
+"(such as security configurations,...). Instead, archive it."
+msgstr ""
+
 #. module: base
 #. odoo-python
 #: code:addons/base/models/res_lang.py:0

odoo/addons/base/models/res_users.py

@@ -701,6 +701,9 @@ class Users(models.Model):
         default_user_template = self.env.ref('base.default_user', False)
         if SUPERUSER_ID in self.ids:
             raise UserError(_('You can not remove the admin user as it is used internally for resources created by Odoo (updates, module installation, ...)'))
+        user_admin = self.env.ref('base.user_admin', raise_if_not_found=False)
+        if user_admin and user_admin in self:
+            raise UserError(_('You cannot delete the admin user because it is utilized in various places (such as security configurations,...). Instead, archive it.'))
         self.env.registry.clear_cache()
         if (portal_user_template and portal_user_template in self) or (default_user_template and default_user_template in self):
             raise UserError(_('Deleting the template users is not allowed. Deleting this profile will compromise critical functionalities.'))