[FIX] mass_mailing*: made demo mailing editable

*: _sale, _crm

Steps to reproduce:

- install Email Marketing
- duplicate an existing demo template
- edit > drag a block from the editor onto the email

Issue:
`Traceback: Uncaught Promise > Cannot read properties of undefined
(reading 'droppable')`

This happens because the email templates are not editable, which means no dropzones can be attached to them.

Solution:
Add classes 'oe_structure' and 'o_editable' to one div in the
templates so that at least one dropzone can be created.

opw-3050732

closes odoo/odoo#111161

X-original-commit: 5f19f9c33656d8b38e827383e0dc8d65e5ebad2a
Signed-off-by: Stefan-Calin Crainiciuc (stcc) <stcc@odoo.com>

addons/mass_mailing/data/mass_mailing_demo.xml

@@ -89,7 +89,7 @@
 <div class="o_layout o_default_theme oe_unremovable oe_unmovable" data-name="Mailing">
     <div class="container o_mail_wrapper oe_unremovable oe_unmovable" style="border-collapse:collapse;">
         <div class="row">
-            <div class="col o_mail_no_options o_mail_wrapper_td bg-white oe_structure" style="text-align:left;width:100%;">
+            <div class="col o_mail_no_options o_mail_wrapper_td bg-white oe_structure o_editable" style="text-align:left;width:100%;">
                 <div class="o_mail_block_header_logo" data-snippet="s_mail_block_header_logo">
                     <div class="o_mail_snippet_general" style="margin:0px auto 0px auto;background-color:rgb(255, 255, 255);max-width:600px;width:100%;">
                         <div class="container o_mail_h_padding" style="padding:0 20px 0 20px;width:100%;border-collapse:separate;">

addons/mass_mailing_crm/data/mass_mailing_demo.xml

@@ -14,6 +14,7 @@
         <field name="reply_to_mode">new</field>
         <field name="reply_to">{{ object.company_id.email }}</field>
         <field name="body_html" type="html">
+<div class="oe_structure o_editable">
 <table border="0" cellpadding="0" cellspacing="0" style="padding-top: 16px; background-color: #F1F1F1; font-family:Verdana, Arial,sans-serif; color: #454748; width: 100%; border-collapse:separate;"><tr><td align="center">
 <table border="0" cellpadding="0" cellspacing="0" width="590" style="padding: 24px; background-color: white; color: #454748; border-collapse:separate;">
 <tbody>
@@ -72,7 +73,7 @@
 <tr><td align="center" style="min-width: 590px;">
         Powered by <a target="_blank" href="https://www.odoo.com?utm_source=db&amp;utm_medium=email" style="color: #875A7B;">Odoo</a>
 </td></tr>
-</table></field>
+</table></div></field>
     </record>
 </data>
 </odoo>

addons/mass_mailing_sale/data/mass_mailing_demo.xml

@@ -14,6 +14,7 @@
         <field name="reply_to_mode">new</field>
         <field name="reply_to">{{ object.company_id.email }}</field>
         <field name="body_arch" type="html">
+<div class="oe_structure o_editable">
 <table border="0" cellpadding="0" cellspacing="0" style="padding-top: 16px; background-color: #F1F1F1; font-family:Verdana, Arial,sans-serif; color: #454748; width: 100%; border-collapse:separate;"><tr><td align="center">
 <table border="0" cellpadding="0" cellspacing="0" width="590" style="padding: 24px; background-color: white; color: #454748; border-collapse:separate;">
 <tbody>
@@ -72,7 +73,7 @@
 <tr><td align="center" style="min-width: 590px;">
         Powered by <a target="_blank" href="https://www.odoo.com?utm_source=db&amp;utm_medium=email" style="color: #875A7B;">Odoo</a>
 </td></tr>
-</table></field>
+</table></div></field>
     </record>
 </data>
 </odoo>