[FIX] website: fix editor not starting after creating a website

Commit [1] introduced an automatic start of edit mode when
selecting a theme but didn't take into account wether the frontend lang
of the user was matching that of the website that is supposed to enter
in edit mode.

Steps to reproduce:
- Create an empty database and install website.
- Add an extra lang on website (e.g FR) and visit the website in that
lang.
- Go in settings an create a new website, skiper the configurator,
  select a theme.
- Redirect is with enable_editor but nothing happens.

The editor isn't started if not in the source's lang.

This commit redirect the user to the default_lang of the website
so that editor can always be started. It also introduces a tour
to test out the flow.

[1]: https://github.com/odoo/odoo/commit/f474eac4543712ae5b1c7d614f9eff9367445107

task-2687416

closes odoo/odoo#85058

X-original-commit: 02e08af7278cd66d768fe6a4f23aa17eb816be3c
Signed-off-by: Romain Derie (rde) <rde@odoo.com>

addons/website/tests/test_automatic_editor.py

@@ -0,0 +1,17 @@
+from odoo.tests import tagged
+from odoo.addons.website.tests.test_configurator import TestConfiguratorCommon
+
+@tagged('post_install', '-at_install')
+class TestAutomaticEditor(TestConfiguratorCommon):
+
+    def test_01_automatic_editor_on_new_website(self):
+        # We create a lang because if the new website is displayed in this lang
+        # instead of the website's default one, the editor won't automatically
+        # start.
+        self.env['res.lang'].create({
+            'name': 'Parseltongue',
+            'code': 'pa_GB',
+            'iso_code': 'pa_GB',
+            'url_code': 'pa_GB',
+        })
+        self.start_tour('/', 'automatic_editor_on_new_website', login='admin')