saml adapters docs/dist

docbook/auth-server-docs/reference/en/en-US/master.xml

@@ -94,6 +94,12 @@ This one is short
             types are supported and how to configure and install them so that you can use Keycloak to secure
             your applications.
         </para>
+        <para>
+            These client adapters use an extension of the OpenID Connect protocol (a derivate of OAuth 2.0).
+            This extension provides support for clustering, backchannel logout, and other non-standard adminstrative functions.
+            The Keycloak project also provides a separate, standalone, generic, SAML client adapter.  But that is describe in a separate
+            document and has a different download.
+        </para>
         &AdapterConfig;
         &JBossAdapter;
         &TomcatAdapter;