[IMP] test_website: add a test for 308 redirect with multi url route

This commit introduces a test in Odoo 15 about a broken behavior in Odoo
16 which was not covered by a test.
A fix will be shipped alongside this commit forward-port in Odoo 16.

The behavior involved here is about:
- Having a multi-url defined route
- One of those URL not having a model converter
- One of those URL having a model converter
- Creating a 308 redirect for the URL without model converter

Something like this route (real example from the code):
```py
@http.route([
    '''/shop''',
    '''/shop/page/<int:page>''',
    '''/shop/category/<model("product.public.category"):category>''',
    '''/shop/category/<model("product.public.category"):category>/page/<int:page>'''
], type='http', auth="public", website=True, sitemap=sitemap_shop)
```
And this redirect (real usual example from clients):
```py
self.env['website.rewrite'].create({
    'name': 'Test Multi URL 308',
    'redirect_type': '308',
    'url_from': '/shop',
    'url_to': '/magasin',
})
```

In Odoo 15, everything will work as expected:
1. Accessing /shop will redirect to /magasin
2. Accessing /shop/category/categ-1 will not redirect and user will be
   on /shop/category/categ-1 still

But in Odoo 16:
In the case described above, acessing the URL with model converter from
the route will fail and redirect to a non slugified URL in the form of
`/some-url?param=test.model%287%2C%29` which is basically the
stringified encoded version of the record `test.model(7,)`.

Note:
- It doesn't matter if the route is contained in the other, the error
  will still occur even if `'''/shop'''` was `'''/abc'''`.
- Even if all URL from the route have their own 308 redirect, the error
  will still occur.
- It won't have any issue if there is a 308 on the route with model
  converter: both the one without model converter and other url with
  model converter will work and won't be impacted.

This might be because of a concept of "merging URL" from httpocalypse,
see https://github.com/odoo/odoo/commit/347a3ccf763cc6958d5dc1df3168c9c65245736c

opw-3450054
opw-3466498
opw-3477380
opw-3475694

X-original-commit: 22ca1c48f78cdf575f9a2b0823f9487f942bc7cd
Part-of: odoo/odoo#134206

addons/test_website/controllers/main.py

@@ -143,6 +143,13 @@ class WebsiteTest(Home):
     def test_redirect_view_qs(self, **kw):
         return request.render('test_website.test_redirect_view_qs')
 
+    @http.route([
+        '/test_countries_308',
+        '/test_countries_308/<model("test.model"):rec>',
+    ], type='http', auth='public', website=True, sitemap=False)
+    def test_countries_308(self, **kwargs):
+        return request.make_response('ok')
+
     # Test Sitemap
     def sitemap_test(env, rule, qs):
         if not qs or qs.lower() in '/test_website_sitemap':

addons/test_website/tests/test_redirect.py

@@ -231,3 +231,24 @@ class TestRedirect(HttpCase):
         r = self.url_open(url_rec1, allow_redirects=True)
         self.assertEqual(r.status_code, 200)
         self.assertTrue(r.url.endswith(redirect.url_to))
+
+    def test_redirect_308_multiple_url_endpoint(self):
+        self.env['website.rewrite'].create({
+            'name': 'Test Multi URL 308',
+            'redirect_type': '308',
+            'url_from': '/test_countries_308',
+            'url_to': '/test_countries_308_redirected',
+        })
+        rec1 = self.env['test.model'].create({
+            'name': '301 test record',
+            'is_published': True,
+        })
+        url_rec1 = f"/test_countries_308/{slug(rec1)}"
+
+        resp = self.url_open("/test_countries_308", allow_redirects=False)
+        self.assertEqual(resp.status_code, 308)
+        self.assertEqual(resp.headers.get('Location'), self.base_url() + "/test_countries_308_redirected")
+
+        resp = self.url_open(url_rec1)
+        self.assertEqual(resp.status_code, 200)
+        self.assertTrue(resp.url.endswith(url_rec1))