Add Missing Navigation In Preparing for 7.0 Guide

Closes gh-17731

docs/modules/ROOT/nav.adoc

@@ -7,7 +7,9 @@
 ** xref:migration-7/authorization.adoc[Authorization]
 ** xref:migration-7/configuration.adoc[Configuration]
 ** xref:migration-7/ldap.adoc[LDAP]
+** xref:migration-7/messaging.adoc[Messaging]
 ** xref:migration-7/oauth2.adoc[OAuth 2.0]
+** xref:migration-7/saml2.adoc[SAML 2.0]
 ** xref:migration-7/web.adoc[Web]
 * xref:migration/index.adoc[Migrating to 6]
 * xref:getting-spring-security.adoc[Getting Spring Security]