KEYCLOAK-7094 Support redirect to external logout page

securing_apps/topics/saml/java/general-config/sp_element.adoc

@@ -56,3 +56,9 @@ autodetectBearerOnly::
   but send an HTTP `401` status code to unauthenticated SOAP or REST clients instead as they would not understand a redirect to the login page.
   Keycloak auto-detects SOAP or REST clients based on typical headers like `X-Requested-With`, `SOAPAction` or `Accept`.
   The default value is _false_.
+
+logoutPage::
+  This sets the page to display after logout. If the page is a full URL, such as `http://web.example.com/logout.html`,
+  the user is redirected after logout to that page using the HTTP `302` status code. If a link without scheme part is specified,
+  such as `/logout.jsp`, the page is displayed after logout, _regardless of whether it lies in a protected area according
+  to `security-constraint` declarations in web.xml_, and the page is resolved relative to the deployment context root.

tests/src/test/resources/ignored-links

@@ -13,4 +13,5 @@ http://node11:8080/auth/
 http://node12:8080*
 http://node21:8080*
 http://node22:8080*
+http://web.example.com*
 https://github.com/keycloak/keycloak-documentation/blob/master/*