[IMP] point_of_sale: Configure https in the POS

The default protocol int the POS with "other device"
is on HTTP.

This doc explain how to activate the HTTPS in the POS

content/applications/sales/point_of_sale/overview.rst

@@ -9,3 +9,4 @@ Overview
 
    overview/getting_started
    overview/register
+   overview/https

content/applications/sales/point_of_sale/overview/https.rst

@@ -0,0 +1,30 @@
+===========
+Using HTTPS
+===========
+
+By default, POS loading is done in HTTP 
+if "direct devices" are selected. (ePos printer or six terminal)
+
+Create a system key to force the POS in HTTPS
+=============================================
+
+Load you domain in debug mode to allow you to edit system parameter
+Please refer to the :doc:`Developer Mode </applications/general/developer_mode>`.
+
+To add a key for the system, go to :menuselection:`Settings --> Technical --> Parameters --> System Parameters`
+
+.. image:: media/https01.png
+    :align: center
+
+Create a new key:
+
+**Key**: ``point_of_sale.enforce_https``
+
+**Value**: ``True``
+
+and save it.
+
+.. image:: media/https02.png
+    :align: center
+
+Now your POS will be loaded in HTTPS.