[ADD] inventory: reassign lots/serial numbers

closes odoo/documentation#9227

Signed-off-by: Felicia Kuan (feku) <feku@odoo.com>
Co-authored-by: Jess Rogers <104637850+jero-odoo@users.noreply.github.com>
Co-authored-by: ksc-odoo <73958186+ksc-odoo@users.noreply.github.com>
Co-authored-by: Sam Lieber (sali) <36018073+samueljlieber@users.noreply.github.com>

content/applications/inventory_and_mrp/inventory/product_management/product_tracking.rst

@@ -12,6 +12,7 @@ Product tracking
    product_tracking/create_sn
    product_tracking/serial_numbers
    product_tracking/lots
+   product_tracking/reassign
    product_tracking/expiration_dates
    product_tracking/package
    product_tracking/packaging

content/applications/inventory_and_mrp/inventory/product_management/product_tracking/reassign.rst

@@ -0,0 +1,90 @@
+===========================
+Reassign lot/serial numbers
+===========================
+
+Changing a product's tracking settings to use lots or serial numbers, *after* storing products in
+Odoo without them, can lead to inconsistent records. Follow this documentation to learn how to use
+an inventory adjustment to assign lot or serial numbers to products that were not originally
+assigned lots.
+
+.. image:: reassign/warning.png
+   :align: center
+   :alt: Warning message: products in stock have no lot/serial number.
+
+.. note::
+   This document outlines the process of using two inventory adjustments: one to remove incorrect
+   records *without* lot numbers, and another to save the quantities *with* the lot numbers.
+
+.. seealso::
+   - :doc:`Set up and use lot numbers <lots>`
+   - :doc:`Set up serial numbers <create_sn>`
+   - :doc:`Use serial numbers <serial_numbers>`
+
+Change on-hand quantity to zero
+===============================
+
+To change the product's settings to track by lots or serial numbers, begin by navigating to
+:menuselection:`Inventory app --> Products --> Products`, and select the intended product.
+
+Next, click the product's :guilabel:`On Hand` smart button to open the :guilabel:`Update Quantity`
+page. In the :guilabel:`On Hand Quantity` column, change the value to zero.
+
+.. note::
+   If the product is stored in multiple locations, make sure the **total** on hand quantity at
+   **all** locations is zero.
+
+.. image:: reassign/remove-quant.png
+   :align: center
+   :alt: Show the Inventory Adjustments model, highlighting the "On Hand Quantity" field.
+
+Change traceability setting
+===========================
+
+Return to the product form (:menuselection:`Inventory app --> Products --> Products`), and switch to
+the :guilabel:`Inventory` tab. In the :guilabel:`Traceability` section, change the
+:guilabel:`Tracking` option from :guilabel:`No Tracking` to :guilabel:`By Lots` or :guilabel:`By
+Unique Serial Number`.
+
+.. seealso::
+   :doc:`expiration_dates`
+
+.. image:: reassign/tracking.png
+   :align: center
+   :alt: Enable lots and serial numbers.
+
+Restore on-hand quantity
+========================
+
+After manually changing the on-hand quantity to zero and changing the :guilabel:`Tracking` setting
+to lots or serial numbers, restore the quantities by clicking the :guilabel:`On Hand` smart button
+from the desired product form.
+
+On the :guilabel:`Update Quantity` page, because the on-hand quantity had been previously changed to
+zero, a :guilabel:`No Stock On Hand` warning appears on the page. From here, click the
+:guilabel:`New` button in the top-left corner. Doing so reveals a new, modifiable line on the
+:guilabel:`Update Quantity` page. Then, input a desired lot number in the :guilabel:`Lot/Serial
+Number` field, and adjust the :guilabel:`On Hand Quantity` to its original value.
+
+.. seealso::
+   :doc:`../../warehouses_storage/inventory_management/count_products`
+
+.. image:: reassign/update-quantity.png
+   :align: center
+   :alt: Fill in the "Lot/Serial Number" and "On Hand Quantity" field.
+
+.. tip::
+   To find the original quantity, and adjust the :guilabel:`On Hand Quantity` accordingly, after
+   assigning a new lot or serial number, click the :icon:`fa-pencil` :guilabel:`(pencil)` icon in
+   the :guilabel:`On Hand Quantity` column. Then, click the :icon:`fa-history` :guilabel:`History`
+   button on the far-right.
+
+   .. image:: reassign/adjustment.png
+      :align: center
+      :alt: Show the "History" button on the Inventory Adjustments page.
+
+   The inventory adjustment that changed the on-hand quantity to zero is displayed in the
+   :guilabel:`Quantity` field.
+
+    .. image:: reassign/history.png
+       :align: center
+       :alt: Show the history entry.