[ADD] manufacturing: Unbuild a product

Original doc:https://docs.google.com/document/d/1mSDVpnEx82VvDDgxDrEsN032FFyVnCgSy41lqABkziw/edit

manufacturing/management.rst

@@ -12,3 +12,4 @@ Manufacturing Management
    management/kit_shipping
    management/product_variants
    management/sub_assemblies
+   management/unbuild

manufacturing/management/unbuild.rst

@@ -0,0 +1,39 @@
+=================
+Unbuild a product
+=================
+
+In Odoo Manufacturing App, you can *Unbuild* products. Two use cases
+can be managed: (1) you can unbuild products you have built yourself or
+(2) you can unbuild products you have received.
+
+Let's take the first case, you are manufacturing products yourself. If
+one of your product presents some defect, you might want to unbuild it
+instead of scrapping it completely, allowing you to reuse some
+components of the product.
+
+In the second case, you are buying products for the sole purpose of
+unbuilding them and recycling them.
+
+Unbuild Order
+=============
+
+While in the Manufacturing App, under the *Operations* tab you will
+find the menu *Unbuild Orders*.
+
+.. image:: media/unbuild01.png
+    :align: center
+
+When creating a new one, you can either select a MO if you are
+unbuilding something you manufactured or only select a product if you
+are unbuilding something you received.
+
+.. image:: media/unbuild02.png
+    :align: center
+
+When you are done, just click unbuild and the process will be over.
+
+If you unbuild a product that you manufactured before, you will get the
+components from the MO back in stock.
+
+If you unbuild a product you bought, you will get the components from
+the BoM back in stock.