[FIX] website_mail_channel: _send_confirmation_email with company email

Public user by default don't have email. So when you try to subscribe to a
channel in public user (portal don't receive an email), the email cannot be
send and the user see a message:
  "Unable to post message, please configure the sender's email address.

closes odoo/odoo#60867

X-original-commit: 7e40af524cc1b23abab3140377d993f3e93c5cf0
Signed-off-by: Jérémy Kersten (jke) <jke@openerp.com>

addons/website_mail_channel/models/mail_channel.py

@@ -19,7 +19,9 @@ class MailGroup(models.Model):
         return headers
 
     def _send_confirmation_email(self, partner_ids, unsubscribe=False):
-        base_url = self.env['ir.config_parameter'].sudo().get_param('web.base.url')
+        website = self.env['website'].get_current_website()
+        base_url = website.get_base_url()
+
         route = "/groups/%(action)s/%(channel)s/%(partner)s/%(token)s"
         if unsubscribe:
             template = self.env.ref('website_mail_channel.mail_template_list_unsubscribe')
@@ -38,9 +40,13 @@ class MailGroup(models.Model):
                 'partner': partner_id,
                 'token': token,
             })
-            template.with_context(token_url=token_url).send_mail(self.id,
+            template.with_context(token_url=token_url).send_mail(
+                self.id,
                 force_send=True,
-                email_values={'recipient_ids': [(4, partner_id)]}
+                email_values={
+                    'recipient_ids': [(4, partner_id)],
+                    'email_from': website.company_id.email,
+                }
             )
 
         return True