[Ruby] CRUD - Upsert (#164)

* DOCSP-51932: v2.21.2 patch release (#163)

* add upsert section

* reference

* LM feedback

* checkout snooty

---------

Co-authored-by: Nora Reidy <[email protected]>

Author: rachel-mack

source/crud/update.txt

@@ -105,6 +105,19 @@ where the value of the ``name`` field is ``"Starbucks"``. The update document us
 
       11 document(s) updated
 
+Upsert Option
+~~~~~~~~~~~~~
+	
+The ``upsert`` parameter allows you to use the ``update_one()`` and
+``update_many()`` operations to perform a conditional operation:
+
+- If the specified document exists, the command updates it.
+- If the specified document does not exist, the command creates a new document
+  with the specified parameter.
+
+For more information, see the :ref:`<ruby-upsert-example>` section or the :ref:`options
+table <ruby-update-options-table>` on this page.
+
 Customize the Update Operation
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
@@ -117,6 +130,8 @@ operation with default settings.
 The following table describes the options that you can use to
 configure the update operation:
 
+.. _ruby-update-options-table:
+
 .. list-table::
    :widths: 30 70
    :header-rows: 1
@@ -161,6 +176,8 @@ configure the update operation:
          </reference/command/update/#std-label-update-let-syntax>` in the
          {+mdb-server+} manual.
 
+.. _ruby-upsert-example:
+
 Modify Update Example
 `````````````````````