[ADD] discuss: doc about email template (#598)

discuss.rst

@@ -14,4 +14,5 @@ Discuss
    discuss/team_communication
    discuss/plan_activities
    discuss/mail_twitter
-   discuss/email_servers
+   discuss/email_servers
+   discuss/advanced

discuss/advanced.rst

@@ -0,0 +1,9 @@
+========
+Advanced
+========
+
+.. toctree::
+   :titlesonly:
+   :glob:
+
+   advanced/emailtemplate

discuss/advanced/emailtemplate.rst

@@ -0,0 +1,59 @@
+===============
+Email Templates
+===============
+
+We all know writing good emails is vital to get a high response rate, but you do not want to
+rewrite the same structure every time, do you? That is where email templates come in.
+Without the need to rewrite the entire email structure every time, you save time to focus on
+the content. Multiple templates also let you deliver the right message to the right audience,
+improving their overall experience with the company.
+
+Enable it and understand a few concepts
+=======================================
+
+The :doc:`Developer mode <../../general/developer_mode/activate>` must be activated. Then, go to
+:menuselection:`Settings --> Technical --> Templates`. A view of the existing templates is shown.
+
+.. warning::
+   **It is highly recommended not to change the content in existing templates unless the user has
+   prior knowledge about placeholders.**
+
+To add a new one, click on *Create* and choose the type of document this template is used with. In
+the example below, the template would be sent to job applicants.
+
+.. image:: media/newtemplate.png
+   :align: center
+   :alt: New email template form in Odoo
+
+| Under *Email Configuration*, fields such as *From*, *To (Emails)*, *To (Partners)*, require
+  placeholders. If the *From* field is not set, the default value is the author’s email alias, if
+  configured, or email address.
+| Under *Advanced Settings*, if an *Outgoing Mail Server* is not set, the one with the highest
+  priority is used.
+| The option *Auto Delete* permanently deletes the emails after they are sent, saving space in your
+  database.
+
+Writing content including placeholder expressions
+-------------------------------------------------
+
+Under the tab *Dynamic Placeholder Generator*, look for the *Field* you would like to use.
+
+.. image:: media/placeholders.png
+   :align: center
+   :alt: View of the dynamic placeholder generator tab under a new template in Odoo
+
+Next, copy the *Placeholder Expression* and paste it in the *Body* of the email, under the *Content*
+tab, using - essentially - the *Code View*.
+
+.. image:: media/codeview.png
+   :align: center
+   :alt: View of the body code view under the content tab in Odoo
+
+Deactivate the *Code View* option by simply clicking on it again, and easily design the message.
+Click on *Preview* to check how the email looks before sending it.
+
+.. image:: media/preview.png
+   :align: center
+   :alt: View of the content with the standard body view in Odoo
+
+