docs: adds note about the auto linking flag in LTI Consumer configura…

…tion

A new flag was introduced in the LTI Consumer configuration which allows
automatically linking LTI users with the edX platform users by matching
the email ID. This commit describes the purpose of the flag with its caveats.

Ref: openedx/edx-platform#33310

en_us/install_operations/source/configuration/lti/configure_lti.rst

@@ -52,6 +52,20 @@ follow these steps.
    .. important:: Do not supply a value for the **Instance guid** field. The
       tool consumer generates and supplies a globally unique identifier.
 
+    - **Auto link users using email:** Check this if the learners accessing the
+      content via LTI already have an account in the edX platform using the same
+      email as the LTI Consumer and you want the data they generate (like
+      submissions and grades) on the platform to be associated with that
+      account instead of the Anonymous account that's created by default. This
+      is done by making use of the ``lis_person_contact_primary_email``
+      attribute shared by the LTI Consumer during the LTI Launch and the auto
+      linking will not work if the LTI Consumer does not send this value or sends
+      a default value due to stricter privacy settings.
+
+   .. note:: The **Auto link users using email** field can only set when a new
+        LTI Consumer is created. This helps the LTI Consumer to have consistency
+        in the way it stores learner data.
+
 #. Select **Save** at the bottom of the page.
 
 .. include:: ../../../../links/links.rst