RHIDP-4684 Update Keycloak configuration instructions to improve performance and security

Signed-off-by: Fabrice Flore-Thébault <[email protected]>

Author: themr0c

modules/authentication/proc-enabling-authentication-with-rhsso.adoc

@@ -168,6 +168,20 @@ auth:
 ----
 --
 
+`auth.backstageTokenExpiration`::
+--
+To change {product-short} token expiration from the default value of one hour.
+Note that this is not the session duration, but rather the duration that the short-term cryptographic tokens are valid for.
+You cannot set the expiration value lower than 10 minutes or above 24 hours.
+
+.`app-config-rhdh.yaml` fragment with optional `auth.backstageTokenExpiration` field
+[source,yaml,subs="+quotes"]
+----
+auth:
+  backstageTokenExpiration: { minutes: _<user_defined_value>_ }
+----
+--
+
 --
 
 .Verification