[ADD] point_of_sale: customer display doc page

task-3226201

There was previously no docs for the customer display feature in pos.
In this commit we add a docs page for it

X-original-commit: fa1461021e

content/applications/sales/point_of_sale/shop.rst

@@ -11,3 +11,4 @@ Shop features
    shop/barcode
    shop/serial_numbers
    shop/ship_later
+   shop/customer_display

content/applications/sales/point_of_sale/shop/customer_display.rst

@@ -0,0 +1,49 @@
+================
+Customer display
+================
+
+The **customer display** feature provides customers with real-time checkout updates on a secondary
+display.
+
+.. image:: customer_display/display.png
+   :alt: customer screen
+
+Configuration
+=============
+
+Depending on your POS setup, the feature can be displayed :ref:`locally on a secondary screen
+<customer_display/local>` or on :ref:`another monitor connected to an IoT Box
+<customer_display/iot>`.
+
+To activate the feature, go to the POS settings, scroll down to the :guilabel:`Connected Devices`
+section, and tick the :guilabel:`Customer Display` checkbox.
+
+.. image:: customer_display/feature-setting.png
+   :alt: customer display setting checkbox
+
+.. _customer_display/local:
+
+Local
+-----
+
+Connect a second screen to your POS and :ref:`open a POS session <pos/session-start>`. Then, click
+:guilabel:`Customer Screen` to open a new window to drag and drop onto the second screen.
+
+.. _customer_display/iot:
+
+IoT box
+-------
+
+Connect an IoT box to your database and the second screen to the IoT box. Then, go to
+:menuselection:`Point of Sale --> Configuration --> Settings`, scroll down to the
+:guilabel:`Connected Devices` section, tick the :guilabel:`IoT Box` checkbox, and select the second
+monitor in the :guilabel:`Customer Display` field.
+
+.. image:: customer_display/iot-setting.png
+   :alt: iot setting to connect a customer display
+
+.. note::
+   Both devices need to be connected to the same local network.
+
+.. seealso::
+   :doc:`../../../general/iot/config/pos`