[ADD] point_of_sale: How to create & run a loyalty reward system

https://docs.google.com/document/d/19Ch_qJftN6My194Ei1nxkcJ9J67gqeNeUrhWLhVOC7Q/edit#

point_of_sale/advanced/loyalty.rst

@@ -1,3 +1,103 @@
 =============================================
 How to create & run a loyalty & reward system
 =============================================
+
+Configuration
+=============
+
+In the **Point of Sale** application, go to 
+:menuselection:`Configuration --> Settings`.
+
+.. image:: media/loyalty01.png
+    :align: center
+
+You can tick **Manage loyalty program with point and reward for
+customers**.
+
+.. image:: media/loyalty02.png
+    :align: center
+
+Create a loyalty program
+========================
+
+After you apply, go to :menuselection:`Configuration --> Loyalty Programs`
+and click on **Create**.
+
+.. image:: media/loyalty03.png
+    :align: center
+
+Set a **name** and an **amount** of points given **by currency**, 
+**by order** or **by product**. Extra rules can also be added 
+such as **extra points** on a product.
+
+To do this click on **Add an item** under **Rules**.
+
+.. image:: media/loyalty04.png
+    :align: center
+
+You can configure any rule by setting some configuration values.
+
+-   **Name**: An internal identification for this loyalty program rule
+-   **Type**: Does this rule affects products, or a category of products?
+-   **Target Product**: The product affected by the rule
+-   **Target Category**: The category affected by the rule
+-   **Cumulative**: The points won from this rule will be won in addition to other rules
+-   **Points per product**: How many points the product will earn per product ordered
+-   **Points per currency**: How many points the product will earn per value sold
+
+.. image:: media/loyalty05.png
+    :align: center
+
+Your new rule is now created and rewards can be added by clicking on
+**Add an Item** under **Rewards**.
+
+.. image:: media/loyalty06.png
+    :align: center
+
+Three types of reward can be given : **Resale**, **Discount** or **Gift**.
+
+.. image:: media/loyalty07.png
+    :align: center
+
+Applying your loyalty program to a point of sale
+================================================
+
+On the **Dashboard**, click on :menuselection:`More --> Settings`.
+
+.. image:: media/loyalty08.png
+    :align: center
+
+Next to loyalty program, set the program you want to set.
+
+.. image:: media/loyalty09.png
+    :align: center
+
+Gathering and consuming points
+==============================
+
+To start gathering points you need to set a customer on the order.
+
+Click on **Customer** and select the right one.
+
+Loyalty points will appear on screen.
+
+.. image:: media/loyalty10.png
+    :align: center
+
+The next time the customer comes to your shop and has enough points to
+get a reward, the **Rewards** button is highlighted and gifts can be
+given.
+
+.. image:: media/loyalty11.png
+    :align: center
+
+The reward is added and of course points are subtracted from the total.
+
+.. image:: media/loyalty12.png
+    :align: center
+
+.. seealso::
+    * :doc:`../shop/cash_control`
+    * :doc:`../shop/invoice`
+    * :doc:`../shop/refund`
+    * :doc:`../shop/seasonal_discount`