[ADD] inventory: How to use different units of measure?

https://docs.google.com/document/d/1-Zx_5TUujZjfghGQMf_ex7RKihltStVswqUrGcIJ7E8/edit#heading=h.cw6sbnjkys37

inventory/settings/products.rst

@@ -7,3 +7,4 @@ Products
    :glob:
 
    products/variants
+   products/uom

inventory/settings/products/uom.rst

@@ -0,0 +1,129 @@
+======================================
+How to use different units of measure?
+======================================
+
+Overview
+========
+
+In some cases, handling products in different unit of measures is
+necessary. For example, if you buy products in a country where the
+metric system is of application and sell the in a country where the
+imperial system is used, you will need to convert the units.
+
+You can set up Odoo to work with different units of measure for one
+product.
+
+Configuration
+=============
+
+In the **Inventory** application, go to :menuselection:`Configuration --> Settings`.
+In the **Products** section, select **Some products may be sold/purchased in
+different units of measure (advanced)**, then click on **Apply**.
+
+.. image:: media/uom09.png
+   :align: center
+
+Setting up units on your products
+=================================
+
+In :menuselection:`Inventory Control --> Products`, open the product which you would like to
+change the purchase/sale unit of measure, and click on **Edit**.
+
+In the **Unit of Measure** section, select the unit in which the product
+will be sold and in which internal transfers will be done.
+
+In the **Purchase Unit of Measure** section, select the unit in which
+you purchase the product. When you’re done, click on **Save**.
+
+.. image:: media/uom10.png
+   :align: center
+
+.. tip::
+    Click on the edit button |edit| to create new unit of measures.
+
+
+Transfer from one unit to another
+=================================
+
+When doing inter-unit transfers, the rounding is automatically done by
+Odoo.
+
+The unit of measure can be changed throughout the whole process. The
+only condition is that the unit of measure is part of the same category.
+
+In this example, we are in the egg business :
+
+-  We buy eggs by trays (30 eggs)
+
+-  We check all eggs individually when receiving it (quality control)
+
+-  We sell eggs by the dozen to the customers
+
+.. image:: media/uom01.png
+   :align: center
+
+.. note::
+    The **Sale price** is expressed in the **Product unit of measure**. The
+    **Cost price** is expressed in the **Purchase Unit of Measure**.
+
+.. note::
+    All internal transfers are expressed in the **Product Unit of
+    Measure**.
+
+Procurement
+-----------
+
+When doing your procurement request, you can still change the unit of
+measure.
+
+.. image:: media/uom06.png
+   :align: center
+
+The unit of measure can also be changed in the purchase order :
+
+.. image:: media/uom03.png
+   :align: center
+
+Quality Control
+---------------
+
+The quality control is done by unit.
+
+The basic unit of measure of our product is **Unit**. Therefore the
+quality check is done by unit.
+
+.. image:: media/uom05.png
+   :align: center
+
+.. note::
+    The unit of measure can only be changed when the transfer status
+    is **Draft**.
+
+Delivery process
+----------------
+
+The eggs are sold by the dozen. You can choose the unit of measure on
+the sale order document. When doing it, the price is automatically
+computed from the unit to the dozen.
+
+.. image:: media/uom04.png
+   :align: center
+
+In the delivery order, the initial demand is done in the sales order unit
+of measure :
+
+.. image:: media/uom02.png
+   :align: center
+
+But the transfer is done in the product unit of measure. Everything is
+converted automatically :
+
+.. image:: media/uom08.png
+   :align: center
+
+.. todo::
+    Create a link when the document is available
+    -  When should you use packages, units of measure or kits?
+
+
+.. |edit| image:: ./media/uom07.png