[IMP] website_mail_channel: unsubscribing unsubscribed address

Before this fix, if a (non-registered) user tried to unsubscribe an
address *not registered*, they'd get an unsub link, click on it, and
get a "Invalid or expired confirmation link." message, usually
wondering what the bloody hell happened.

Provide a clearer message in that case.

addons/website_mail_channel/controllers/main.py

@@ -6,7 +6,7 @@ import werkzeug
 from datetime import datetime
 from dateutil import relativedelta
 
-from odoo import http, fields, tools
+from odoo import http, fields, tools, _
 from odoo.http import request
 from odoo.addons.website.models.website import slug
 
@@ -228,8 +228,16 @@ class MailGroup(http.Controller):
     def confirm_unsubscribe(self, channel, partner_id, token, **kw):
         subscriber = request.env['mail.channel.partner'].search([('channel_id', '=', channel.id), ('partner_id', '=', partner_id)])
         if not subscriber:
-            # not registered, maybe already unsubsribed
-            return request.render('website_mail_channel.invalid_token_subscription')
+            # FIXME: remove try/except in master
+            try:
+                return request.render(
+                    'website_mail_channel.not_subscribed', {
+                    'partner_id': partner_id
+                })
+            except ValueError:
+                return _("The address %s is already unsubscribed or was never subscribed to any mailing list") % (
+                    partner_id.email
+                )
 
         subscriber_token = channel._generate_action_token(partner_id, action='unsubscribe')
         if token != subscriber_token:

addons/website_mail_channel/i18n/website_mail_channel.pot

@@ -291,3 +291,18 @@ msgstr ""
 msgid "your email..."
 msgstr ""
 
+#. module: website_mail_channel
+#: model:ir.ui.view,arch_db:website_mail_channel.not_subscribed
+msgid "The address"
+msgstr ""
+
+#. module: website_mail_channel
+#: model:ir.ui.view,arch_db:website_mail_channel.not_subscribed
+msgid "is already unsubscribed or was never subscribed to the mailing list, you may want to check that the address was correct."
+msgstr ""
+
+#. module: website_mail_channel
+#: code:addons/website_mail_channel/controllers/main.py:238
+#, python-format
+msgid "The address %s is already unsubscribed or was never subscribed to any mailing list"
+msgstr ""

addons/website_mail_channel/views/website_mail_channel_templates.xml

@@ -338,4 +338,19 @@
     </t>
 </template>
 
+<template id="not_subscribed" name="Email address was not subscribed">
+    <t t-call="website.layout">
+        <div id="wrap" class="oe_structure oe_empty">
+            <div class="container">
+                <p>
+                    The address <t t-esc="partner_id.email"/> is already
+                    unsubscribed or was never subscribed to the mailing
+                    list, you may want to check that the address was
+                    correct.
+                </p>
+            </div>
+        </div>
+    </t>
+</template>
+
 </odoo>