[IMP] mass_mailing: use mail thread link replacer

Mail thread now holds a method to replace local links by global links.
Let us therefore use it in mass mailing as it does basically the same
job. Adding base tag is not necessary anymore since there are not
local links or images anymore.

addons/mass_mailing/models/mail_mail.py

@@ -71,15 +71,7 @@ class MailMail(models.Model):
                     new_href = href.replace(url, url + '/m/' + str(self.statistics_ids[0].id))
                     body = body.replace(href, new_href)
 
-        # prepend <base> tag for images using absolute urls
-        domain = self.env["ir.config_parameter"].sudo().get_param("web.base.url")
-        base = "<base href='%s'>" % domain
-        body = tools.append_content_to_html(base, body, plaintext=False, container_tag='div')
-        # resolve relative image url to absolute for outlook.com
-        def _sub_relative2absolute(match):
-            return match.group(1) + werkzeug.urls.url_join(domain, match.group(2))
-        body = re.sub('(<img(?=\s)[^>]*\ssrc=")(/[^/][^"]+)', _sub_relative2absolute, body)
-        body = re.sub(r'(<[^>]+\bstyle="[^"]+\burl\(\'?)(/[^/\'][^\'")]+)', _sub_relative2absolute, body)
+        body = self.env['mail.thread']._replace_local_links(body)
 
         # generate tracking URL
         if self.statistics_ids: