[REF] refactor the code in order to split it in several file

mail_usability/wizard/email_template_preview_view.xml

@@ -0,0 +1,24 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<odoo>
+
+<record id="email_template_preview_form" model="ir.ui.view">
+    <field name="model">email_template.preview</field>
+    <field name="inherit_id" ref="mail.email_template_preview_form"/>
+    <field name="arch" type="xml">
+        <field name="res_id" position="attributes">
+            <attribute name="invisible">True</attribute>
+        </field>
+        <field name="res_id" position="after">
+            <field name="object_id"/>
+        </field>
+        <footer position="inside">
+            <button
+                string="Send"
+                name="send"
+                class="btn-primary"
+                type='object'/>
+        </footer>
+    </field>
+</record>
+
+</odoo>