old_contents: # Copyright 2018 Simone Orsi <simone.orsi@camptocamp.com>
  # Copyright initOS GmbH 2016
  # License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl).
  
  from odoo import models, api, fields, exceptions, _
  from odoo.http import request
  from urllib.parse import urlparse, urljoin
  
  
  class Website(models.Model):
      _inherit = 'website'
  
      canonical_domain = fields.Char(
          help='Canonical domain is used to build unique canonical URLs '
               'to make SEO happy.'
      )
  
      @api.constrains('canonical_domain')
      def _check_canonical_domain(self):
          domain = self.canonical_domain
          if domain and not urlparse(domain).scheme:
              raise exceptions.ValidationError(_(
                  'Canonical domain must contain protocol `http(s)://`'
              ))
  
      @api.multi
      def get_canonical_url(self, req=None):
          return urljoin(
              self._get_canonical_domain(),
              self._get_canonical_relative_url(req=req)
          )
  
      @api.multi
      def _get_canonical_domain(self):
          self.ensure_one()
          if self.canonical_domain:
              return self.canonical_domain
          params = self.env['ir.config_parameter'].sudo()
          return params.get_param('web.base.url')
  
      @api.multi
      def _get_canonical_relative_url(self, req=None):
          req = req or request
          url = req.httprequest.path
          lang_path = '/'
          if req.lang != req.website.default_lang_code:
              lang_path = '/%s/' % req.lang
              # enforce language path
              url = lang_path.rstrip('/') + url
          if self._is_root_page(req.httprequest.path):
              # special case for main menu items: point always to root
              url = lang_path
          return url
  
      def _is_root_page(self, url):
          return (
              self.menu_id.child_id and
              self.menu_id.child_id[0].url == url
          )
  
new_contents: # Copyright 2018 Simone Orsi <simone.orsi@camptocamp.com>
  # Copyright initOS GmbH 2016
  # License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl).
  
  from odoo import models, api, fields, exceptions, _
  from odoo.http import request
  from urllib.parse import urlparse, urljoin
  
  
  class Website(models.Model):
      _inherit = 'website'
  
      canonical_domain = fields.Char(
          help='Canonical domain is used to build unique canonical URLs '
               'to make SEO happy.'
      )
  
      @api.constrains('canonical_domain')
      def _check_canonical_domain(self):
          domain = self.canonical_domain
          if domain and not urlparse(domain).scheme:
              raise exceptions.ValidationError(_(
                  'Canonical domain must contain protocol `http(s)://`'
              ))
  
      @api.multi
      def get_canonical_url(self, req=None):
          return urljoin(
              self._get_canonical_domain(),
              self._get_canonical_relative_url(req=req)
          )
  
      @api.multi
      def _get_canonical_domain(self):
          self.ensure_one()
          if self.canonical_domain:
              return self.canonical_domain
          if self.domain:
              return self.domain
          params = self.env['ir.config_parameter'].sudo()
          return params.get_param('web.base.url')
  
      @api.multi
      def _get_canonical_relative_url(self, req=None):
          req = req or request
          url = req.httprequest.path
          lang_path = '/'
          if req.lang != req.website.default_lang_code:
              lang_path = '/%s/' % req.lang
              # enforce language path
              url = lang_path.rstrip('/') + url
          if self._is_root_page(req.httprequest.path):
              # special case for main menu items: point always to root
              url = lang_path
          return url
  
      def _is_root_page(self, url):
          return (
              self.menu_id.child_id and
              self.menu_id.child_id[0].url == url
          )
  
subject: use website domain