[FIX] base: mail signature CSS inlined for icons etc

The mail signature of an user did not inline the CSS like the body of a
message, so for example icons seemed to work but would not be seen
(unless the mail reader had the same font-awesome system).

With this change we inline the signature too.

On edition there was also an issue since the original icon was saved as
data-class which was stripped: so eg. when editing a mail.message with
working icon, the icons would disappear.

opw-2453912

closes odoo/odoo#66372

X-original-commit: 5e093b7a37984c8cc5aa73d1c0f7aa9c9345e6b1
Signed-off-by: Nicolas Lempereur (nle) <nle@odoo.com>

odoo/addons/base/views/res_users_views.xml

@@ -255,7 +255,7 @@
                                     </group>
                                 </group>
                                 <group name="messaging">
-                                    <field name="signature"/>
+                                    <field name="signature" options="{'style-inline': true}"/>
                                 </group>
                             </page>
                         </notebook>
@@ -453,7 +453,7 @@
                                 </group>
                             </group>
                             <group name="signature">
-                                <field name="signature" readonly="0"/>
+                                <field name="signature" readonly="0" options="{'style-inline': true}"/>
                             </group>
                             <group name="status" string="Status" invisible="1">
                                 <field name="company_id" options="{'no_create': True}" readonly="0"

odoo/tools/mail.py

@@ -39,6 +39,7 @@ safe_attrs = clean.defs.safe_attrs | frozenset(
      'data-o-mail-quote',  # quote detection
      'data-oe-model', 'data-oe-id', 'data-oe-field', 'data-oe-type', 'data-oe-expression', 'data-oe-translation-id', 'data-oe-nodeid',
      'data-publish', 'data-id', 'data-res_id', 'data-interval', 'data-member_id', 'data-scroll-background-ratio', 'data-view-id',
+     'data-class',
      ])