[FIX] website_mass_mailing: add missing s_newsletter_list class

Commit [1], combined with commit [2], added a s_newsletter_list class
on two newsletter snippets to move the related newsletter option to the
root node that contains the newsletter subscription input.

The problem is that no migration script was made thus making it
impossible to customize old snippets anymore. We could mark them as
outdated... but it happens that marking a snippet as outdated (by
incrementing the vxml counter for example) is not straightforward
(users that already migrated would not get that XML update).

This creates a widget that tries to fix snippets that were malformed, on
page load. An upgrade script should be made to fix databases and get rid
of this in the future.

opw-3243399
opw-3244080
opw-3246089
opw-3246194
opw-3246435
opw-3248473

closes odoo/odoo#117416

X-original-commit: 8d7eaaf916250086cd2f628bd2f3b07cc825959a
Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>

addons/website_mass_mailing/static/src/js/website_mass_mailing.js

@@ -140,4 +140,25 @@ publicWidget.registry.subscribe = publicWidget.Widget.extend({
         });
     },
 });
+
+/**
+ * This widget tries to fix snippets that were malformed because of a missing
+ * upgrade script. Without this, some newsletter snippets coming from users
+ * upgraded from a version lower than 16.0 may not be able to update their
+ * newsletter block.
+ *
+ * TODO an upgrade script should be made to fix databases and get rid of this.
+ */
+publicWidget.registry.fixNewsletterListClass = publicWidget.Widget.extend({
+    selector: '.s_newsletter_subscribe_form:not(.s_subscription_list), .s_newsletter_block',
+
+    /**
+     * @override
+     */
+    start() {
+        this.$target[0].classList.add('s_newsletter_list');
+        return this._super(...arguments);
+    },
+});
+
 });

addons/website_mass_mailing/views/snippets_templates.xml

@@ -23,6 +23,10 @@
     </xpath>
 </template>
 
+<!--
+Users upgraded from a version lower than 16.0 may have those blocks in their
+database, without the s_newsletter_list class. See fixNewsletterListClass.
+-->
 <template id="s_newsletter_subscribe_form" name="Newsletter">
     <div class="s_newsletter_subscribe_form s_newsletter_list js_subscribe" data-vxml="001" data-list-id="0" data-name="Newsletter Form">
         <div class="input-group">
@@ -33,6 +37,10 @@
     </div>
 </template>
 
+<!--
+Users upgraded from a version lower than 16.0 may have those blocks in their
+database, without the s_newsletter_list class. See fixNewsletterListClass.
+-->
 <template id="s_newsletter_block" name="Newsletter block">
     <section class="s_newsletter_block s_newsletter_list pt32 pb32" data-list-id="0">
         <div class="container">