[ADD] inventory: How to manage multiple packs for the same delivery order?

https://docs.google.com/document/d/1CjjxTBKdfLajjdeOG2OPithCuKlZJL2YSv-6mC-4T30/edit#heading=h.krwcpcf7j2fg

inventory/shipping/operation/multipack.rst

@@ -1,3 +1,84 @@
 =========================================================
 How to manage multiple packs for the same delivery order?
-=========================================================
+=========================================================
+
+Overview
+========
+
+By default, Odoo considers that your delivery is composed of one
+package. But you can easily ship your deliveries with more than one
+package. It is fully integrated with the third-party shippers.
+
+Configuration
+=============
+
+To configure the use of packages, go to the menu
+:menuselection:`Inventory --> Configuration --> Settings`. 
+Locate the **Packages** section and tick **Record
+packages used on packing: pallets, boxes,...**
+
+.. image:: media/multipack03.png
+   :align: center
+
+Click on **Apply** when you are done.
+
+Sale process
+============
+
+Sale order
+----------
+
+.. image:: media/multipack06.png
+   :align: center
+
+Click on a **Delivery Method** to choose the right one.
+
+The price is computed when you **save** the sale order or when you click on
+**Set price**.
+
+Multi-packages Delivery
+-----------------------
+
+The delivery created from the sale order will take the shipping
+information from it.
+
+.. image:: media/multipack07.png
+   :align: center
+
+From here, you can split your delivery into multiple packages.
+
+Choose the quantity you want to put in the first pack in the **Done**
+column, then click on the link **Put in Pack**.
+
+.. image:: media/multipack02.png
+   :align: center
+
+It will automatically create a pack with the requested quantity.
+
+Do the same steps for the other pieces you want to pack in.
+
+.. image:: media/multipack04.png
+   :align: center
+
+Click on **Validate** when you are done.
+
+Multi-packages with a 3rd party-shipper
+---------------------------------------
+
+Once the delivery order is validated, you will receive the tracking
+number. The **carrier Tracking ref** field will automatically be filled.
+Click on the **Tracking** button to check your delivery on the provider
+website.
+
+.. image:: media/multipack05.png
+   :align: center
+
+The **labels** to stick on your packages are available in the history
+underneath:
+
+.. image:: media/multipack01.png
+   :align: center
+
+.. seealso::
+    * :doc:`invoicing`
+    * :doc:`labels`