[FIX] website: use public user for sitemap making (up to s14)

The current user was used to generate the sitemap. So if a user with
more permissions than `public user` goes on the sitemap, he could
generate it (if he is the first to see it or the last generation was
more than 12 hours ago (by default)) and have pages unavailables for
a user with lower permission in the sitemap (until the sitemap is
generated again).

The issue was solved in 8.0 with d08facdcb but was introduced back in
10.0 with fd09ddb6f because the `uid` argument was dropped from
`generate` method on `ModelConverter`.

From 10.0 up to saas-14 the fix introduced is to use a `use_public_user`
key in `request.context` but in master we will keep the fd09ddb6f fix
by adding uid to the `generate` method.

opw-708456

note: to forward-port only up to saas-14

addons/website/controllers/main.py

@@ -168,7 +168,7 @@ class Website(Home):
             sitemaps.unlink()
 
             pages = 0
-            locs = request.website.sudo(user=request.website.user_id.id).enumerate_pages()
+            locs = request.website.with_context(use_public_user=True).enumerate_pages()
             while True:
                 values = {
                     'locs': islice(locs, 0, LOC_PER_SITEMAP),

addons/website/models/ir_http.py

@@ -363,6 +363,8 @@ class ModelConverter(ir.ir_http.ModelConverter):
 
     def generate(self, query=None, args=None):
         Model = request.env[self.model]
+        if request.context.get('use_public_user'):
+            Model = Model.sudo(request.website.user_id.id)
         domain = safe_eval(self.domain, (args or {}).copy())
         if query:
             domain.append((Model._rec_name, 'ilike', '%' + query + '%'))