[ADD] Sales: New accessory products page

Co-authored-by: Jess Rogers <jero@odoo.com>

content/applications/sales/sales/products_prices.rst

@@ -12,3 +12,4 @@ Products & Prices
    products_prices/returns
    products_prices/ewallets_giftcards
    products_prices/loyalty_discount
+   products_prices/accessory_products

content/applications/sales/sales/products_prices/accessory_products.rst

@@ -0,0 +1,56 @@
+==================
+Accessory products
+==================
+
+The use of accessory products is a marketing strategy that involves the cross-selling of related
+products alongside a desired core product. In Odoo, accessory products can be added to a core
+product's product form to integrate them into the customer's shopping experience and help drive
+increased sales.
+
+.. example::
+
+   An electronics business has configured their products with an eye on cross-selling accessories
+   whenever customers purchase big-ticket items. After a customer adds a tablet to their shopping
+   cart, they are automatically suggested useful accessories like cases, screen protectors,
+   and extra cables because of the accessory products that have been configured. This helps to drive
+   sales by creating opportunities for impulse purchases, as well as reminding customers of useful
+   accessories that they may have intended to purchase but forgot about while shopping.
+
+.. note::
+   Accessory products are differentiated from optional products and alternative products by where
+   they appear in the customer's shopping experience.
+
+   - Accessory products appear as suggestions when viewing an eCommerce cart with an associated core
+     product in it. This creates an opportunity for cross-selling during the checkout process.
+   - Optional products are suggested when a core product has been added to a cart or a quotation.
+     This creates an opportunity for cross-selling during the shopping process.
+   - Alternative products are suggested at the bottom of an eCommerce product page whenever the
+     product page is viewed. This creates an opportunity for upselling during the shopping process.
+
+Configuring accessory products
+==============================
+
+To add an accessory product to a product form, navigate to :menuselection:`Sales --> Products -->
+Products` and choose a product. Ensure that the product's :guilabel:`Sales` checkbox is ticked and
+click the :guilabel:`Sales` tab. Under :guilabel:`Upsell & Cross-sell` heading, the
+:guilabel:`Accessory Products` drop-down menu allows for accessory products to be set. Products will
+be displayed in alphabetical order. If the desired product isn't readily visible, type its name in
+the field to bring it up, then select it to add it as an accessory product.
+
+.. image:: accessory_products/accessory-products-product-form.png
+   :alt: The accessory products section of product forms in Odoo Sales
+
+How accessory products appear to customers
+==========================================
+
+Accessory products appear alongside core products prior to checkout.They are automatically suggested
+based on what accessory products have been configured and what core products the customer has added
+to their shopping cart.
+
+.. figure:: accessory_products/accessory-products-ecommerce.png
+   :alt: A screenshot of an eCommerce shopping cart showing accessory products.
+
+   Accessory products as they appear in an eCommerce website shopping cart.
+
+.. seealso::
+   :doc:`../../../websites/ecommerce/products/cross_upselling`