[FIX] website_forum: fix the invalid URL link

How to reproduce:
- Login as a portal user, create a new post by adding a URL link
- Post Your Question
- Login as admin to validate the post
- Click on 'To Validate' from the moderation tool
- Click on the mentioned URL

Throws a Traceback and redirects to the about:blank#blocked
page.

Technical Reason:
The '_update_content' method performs a regular expression
on the link by using the escape method, which is later convert
the backslash '\' into '%5C' while html_sanitize.

After this commit:
Clicking on the mentioned link redirects to the correct URL

Task-3472776

closes odoo/odoo#148064

X-original-commit: dedfb9a42e7bade98756e73a3d6c54c581e99547
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>

addons/website_forum/models/forum_post.py

@@ -426,8 +426,10 @@ class Post(models.Model):
         forum = self.env['forum.forum'].browse(forum_id)
         if content and self.env.user.karma < forum.karma_dofollow:
             for match in re.findall(r'<a\s.*href=".*?">', content):
-                match = re.escape(match)  # replace parenthesis or special char in regex
-                content = re.sub(match, match[:3] + 'rel="nofollow" ' + match[3:], content)
+                escaped_match = re.escape(match)  # replace parenthesis or special char in regex
+                url_match = re.match(r'^.*href="(.*)".*', match) # extracting the link allows to rebuild a clean link tag
+                url = url_match.group(1)
+                content = re.sub(escaped_match, f'<a rel="nofollow" href="{url}">', content)
 
         if self.env.user.karma < forum.karma_editor:
             filter_regexp = r'(<img.*?>)|(<a[^>]*?href[^>]*?>)|(<[a-z|A-Z]+[^>]*style\s*=\s*[\'"][^\'"]*\s*background[^:]*:[^url;]*url)'

addons/website_forum/tests/test_forum_internals.py

@@ -145,3 +145,14 @@ class TestTags(TestForumCommon):
 
         self.assertEqual(self.base_forum.tag_most_used_ids, self.base_forum.tag_ids[:MOST_USED_TAGS_COUNT])
         self.assertEqual(self.base_forum.tag_unused_ids, self.env['forum.tag'])
+
+    def test_forum_post_link(self):
+        content = 'This is a test link: <a href="https://www.example.com/route?param1=a&param2=b" rel="ugc">test</a> Let make sure it works.'
+        self.user_portal.karma = 50
+        with self.with_user(self.user_portal.login):
+            post = self.env['forum.post'].create({
+                'name': "Post Forum test",
+                'content': content,
+                'forum_id': self.forum.id,
+            })
+        self.assertEqual(post.content, '<p>This is a test link: <a rel="nofollow" href="https://www.example.com/route?param1=a&amp;param2=b">test</a> Let make sure it works.</p>')