[ADD] Sales: Created a new alternative products page

Co-authored-by: Megan Valenzuela <meval@odoo.com>

Author: theRealThagomizer

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/alternative_products

content/applications/sales/sales/products_prices/alternative_products.rst

@@ -0,0 +1,51 @@
+====================
+Alternative products
+====================
+
+The use of alternative products is a marketing strategy that involves upselling related products
+alongside a desired core product. For instance, by configuring alternative products, a customer
+could be suggested a mechanical keyboard or a wireless keyboard when they visit the eCommerce
+website page for a standard keyboard.
+
+Alternative products are automatically suggested during the shopping process whenever a customer
+visits the webpage for an associated core product.
+
+.. image:: alternative_products/product-form-alternative-products.png
+   :alt: The alternative product field on the product form
+
+.. image:: alternative_products/alternative-products-ecommerce.png
+   :alt: Alternative products as they appear on an eCommerce website
+
+.. note::
+   Alternative products are different from accessory and optional products because of where they
+   show up in the customer's shopping experience.
+
+   - Alternative products are suggested at the bottom of an eCommerce product page whenever the
+     product page is viewed.
+   - Accessory products appear as suggestions when viewing an eCommerce cart.
+   - Optional products are suggested when a core product has been added to a cart or a quotation.
+
+Configuring alternative products
+================================
+
+To add an alternative product to a product form, navigate to :menuselection:`Sales --> Products -->
+Products` and choose a product. Ensure that the product's :guilabel:`Sales` checkbox is checked and
+click the :guilabel:`Sales` tab. In the :guilabel:`UPSELL & CROSS-SELL` section, click the
+:guilabel:`Alternative Products` drop-down menu to set alternative products. Products are 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 alternative product.
+
+To delete an alternative product from the product form, simply click the :icon:`fa-times`
+:guilabel:`(Delete)` icon.
+
+Additional alternative products can also be added to a core product by clicking :guilabel:`Search
+more...`. This opens the :guilabel:`Search: Optional Products` form, which displays all products in
+the catalog and includes the :guilabel:`New` button to create a new product. Multiple products can
+be selected as alternatives at once in this form by clicking their checkboxes and then clicking
+:guilabel:`Select`.
+
+.. image:: alternative_products/search-alternative-products-form.png
+   :alt: The Search: Alternative Products form accessed by clicking Search more...
+
+.. seealso::
+   :doc:`/applications/websites/ecommerce/products/cross_upselling`