Update deploy-manage/users-roles/cluster-or-deployment-auth/pki.md

Co-authored-by: shainaraskas <[email protected]>

Author: ebarlas

deploy-manage/users-roles/cluster-or-deployment-auth/pki.md

@@ -47,7 +47,7 @@ To use PKI in {{es}}, you configure a PKI realm, enable client authentication on
 2. Optional: The username is defined by the [username_pattern](https://docs-v3-preview.elastic.dev/elastic/elasticsearch/tree/main/reference/elasticsearch/configuration-reference/security-settings#ref-pki-settings). If you want to use something other than the CN of the Subject DN as the username, you can use one of the following methods to extract the username:
 
     * {applies_to}`stack: ga 9.1` Extract the username from a specific RDN attribute in the Subject DN.
-	* Specify a regex to extract the desired username. The regex is applied on the Subject DN.
+	* Using the [[username_pattern](elasticsearch://reference/elasticsearch/configuration-reference/security-settings.md#ref-pki-settings) setting, specify a regex to extract the desired username. The regex is applied on the Subject DN.
 
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