[ADD] pos: add a new doc page about sales orders in pos

Task ID: 2622084

closes odoo/documentation#2402

X-original-commit: 53744bea5b
Signed-off-by: Castillo Jonathan (jcs) <jcs@odoo.com>
Co-authored-by: Quentin Celis (qce) <qce@odoo.com>
Co-authored-by: Xavier Plateau (xpl) <xpl@odoo.com>
Co-authored-by: Robin Boisdenghien (robo) <robo@odoo.com>

content/applications/sales/point_of_sale/shop.rst

@@ -9,6 +9,7 @@ Shop Features
 
    shop/invoice
    shop/barcode
+   shop/sales_order
    shop/multicashiers
    shop/reprint
    shop/cash_rounding

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

@@ -0,0 +1,47 @@
+===================
+Sales orders in PoS
+===================
+
+When working in retail, you might need to order products directly from your Point of sale.
+Fortunately, Odoo Point of Sale is fully integrated with Odoo Sales, meaning that you can create a
+sales order and pay for it directly from your point of sale.
+
+Select a sales order
+====================
+
+From the **Point of Sale** application, open a new session. Then, click on
+:guilabel:`Quotations/Orders` to get the complete list of quotations and sales orders created on the
+sales application.
+
+.. image:: salesorder/pos-interface.png
+   :align: center
+   :alt: Quotations and sales order button on the Point of Sale interface
+
+.. note::
+   To ease finding the right sales order, you can filter that list on the **customer** or on the
+   **order reference**. You can also set the customer before clicking on
+   :guilabel:`Quotations/Orders` to reduce the list to one particular customer.
+
+Apply a down payment or settle the order
+========================================
+
+From the list of sales order, select one to make a payment.
+
+.. image:: salesorder/list-of-so.png
+   :align: center
+   :alt: list view of sales orders and quotations
+
+You can either:
+
+- Settle the order **partially**: after clicking on :guilabel:`Apply a down payment`, enter the
+  percentage of down payment you want the customer to pay. Then, click on :guilabel:`ok` and proceed
+  with the order.
+- Settle the order **completely**: click on :guilabel:`Settle the order` to pay for the total of the
+  sales order.
+
+.. note::
+   Once you settle a sales order, the applied down payment is automatically deducted from the total
+   amount.
+
+.. Seealso::
+   - :doc:`/applications/sales/sales/invoicing/down_payment`