[ADD] inventory: How to print shipping labels?

https://docs.google.com/document/d/1VODqXfmHO8eMDl-CGjSiqbEqgFnV2TuXZU2XrGG7K9E/edit#heading=h.8e0u1i7a4o47

inventory/shipping/operation/labels.rst

@@ -1,3 +1,116 @@
 =============================
 How to print shipping labels?
-=============================
+=============================
+
+Overview
+========
+
+Odoo can handle various delivery methods, including third party shippers
+linked with the transportation company tracking system. It allows you to
+manage the transport company, the real prices and the destination. And
+finally, you will be able to print the shipping labels directly from
+Odoo.
+
+Configuration
+=============
+
+Install the shipper company connector module
+--------------------------------------------
+
+In the **Inventory** module, click on :menuselection:`Configuration --> Settings`.
+Under **Shipping Connectors**, flag the transportation companies you want to
+integrate :
+
+.. image:: media/labels03.png
+   :align: center
+
+Then click on **Apply**.
+
+Configure the delivery method
+-----------------------------
+
+To configure your delivery methods, go to the **Inventory** module, click on
+:menuselection:`Configuration --> Delivery Methods`.
+
+The delivery methods for the chosen shippers have been automatically
+created.
+
+.. image:: media/labels01.png
+   :align: center
+
+In the **Pricing** tab, the name of the provider means that the delivery
+will be handled and computed by the shipper system.
+
+The configuration of the shipper is split into two columns :
+
+-   The first one is linked to **your account** (develop key, password,...).
+    For more information, please refer to the provider website.
+
+-   The second column varies according to the **provider**. You can choose
+    the packaging type, the service type, the weight unit...
+
+-  Uncheck **Test Mode** when you are done with the testings.
+
+Company configuration
+---------------------
+
+In order to compute the right price, the provider needs your company
+information. Be sure your address and phone number are correctly
+encoded.
+
+.. image:: media/labels02.png
+   :align: center
+
+To check your information, go to the **Settings** application and click on
+**General Settings**. Click on the first link **Configure your company data**.
+
+Product configuration
+---------------------
+
+The shipper companies need the weight of your product, otherwise the
+price computation cannot be done.
+
+Go the **Sales** module, click on :menuselection:`Sales --> Products`.
+Open the products you want to ship and set a weight on it.
+
+.. image:: media/labels06.png
+   :align: center
+
+.. tip::
+    The weight on the product form is expressed in kilograms.
+    Don't forget to do the conversion if you are used to the imperial
+    measurement system.
+
+How to print shipping labels ? 
+===============================
+
+The delivery order created from the sale order will take the shipping
+information from it, but you can change the carrier if you want to.
+
+If you create a delivery transfer from the inventory module, you can add
+the third party shipper in the additional info tab.
+
+.. image:: media/labels05.png
+   :align: center
+
+Click on **Validate** to receive the tracking number and **the label(s)**.
+
+The label to stick on your package is available in the history
+underneath :
+
+.. image:: media/labels04.png
+   :align: center
+
+Click on it to open the document and print it :
+
+.. image:: media/labels07.png
+   :align: center
+
+.. note::
+    If you are doing multi-packages shippings, most of the time,
+    there will be one label per package. Each label will appear in the
+    delivery history.
+
+.. seealso::
+    * :doc:`invoicing`
+    * :doc:`multipack`