Add paragraph and link to Gradle Jakarta EE migration plugin

grails-doc/src/en/guide/upgrading/upgrading60x.adoc

@@ -206,6 +206,22 @@ If there is a plugin that you require updating, please reach out via https://git
 Spring has switched from javax to https://jakarta.ee/[jakarta] packages.
 Please consult the Spring upgrade guides for the impacts of this change.
 
+Gradle Javax-to-Jakarta EE migration plugins, such as the https://github.com/nebula-plugins/gradle-jakartaee-migration-plugin?tab=readme-ov-file#configuring-the-plugin[gradle-jakartaee-migration-plugin], provide transforms and dependency substitutions to ease the migration from Java EE (`javax.`) to Jakarta EE (`jakarta.`). These plugins can help mitigate upgrade challenges with older dependencies that still use `javax.` until they are updated or replaced with alternative solutions.
+
+To apply and configure the `gradle-jakartaee-migration-plugin` in your `build.gradle`, you can use the following snippet:
+
+[source,groovy]
+.build.gradle
+----
+plugins {
+    id 'com.netflix.nebula.jakartaee-migration' version '0.24.0'
+}
+
+jakartaeeMigration {
+    migrate()
+}
+----
+
 ===== 12.2 Removed libraries/classes
 - The `grails-web-fileupload` library, including its sole class `ContentLengthAwareCommonsMultipartResolver`, has been removed. This change was necessitated by the removal of the superclass `CommonsMultipartResolver` in Spring 6. The `ContentLengthAwareCommonsMultipartResolver` was originally introduced to address a bug in Safari back in 2007, but it is likely no longer needed. Spring has transitioned away from `CommonsMultipartResolver` and now recommends using the built-in support for multipart uploads provided by servlet containers. For more information on handling file uploads in Spring Boot, please refer to the relevant sections of the https://docs.spring.io/spring-boot/how-to/spring-mvc.html#howto.spring-mvc.multipart-file-uploads[Spring Boot documentation] and the https://github.com/spring-projects/spring-framework/wiki/Upgrading-to-Spring-Framework-6.x#web-applications-1[Spring Framework 6 upgrade guide].
 - `org.grails.spring.beans.factory.OptimizedAutowireCapableBeanFactory` was previously deprecated and is now removed.
@@ -264,4 +280,4 @@ Please see ticket https://github.com/apache/grails-gradle-plugin/pull/347[#347]
 
 ===== 12.8 Java 20+ Date Formatting Changes
 
-In Java 20+, https://cldr.unicode.org/downloads/cldr-42[Unicode CLDR42] was implemented which changed the space character preceding the period (AM or PM) in formatted date/time text from a standard space (" ") to a narrow non-breaking space (NNBSP: "\u202F"). Additionally, when using the LONG or FULL timeStyle with dateStyle, the date and time separator has changed from ' at ' to ', '. IE. January 5, 1941, 8:00:00 AM UTC vs. January 5, 1941 at 8:00:00 AM UTC
+In Java 20+, https://cldr.unicode.org/downloads/cldr-42[Unicode CLDR42] was implemented which changed the space character preceding the period (AM or PM) in formatted date/time text from a standard space (" ") to a narrow non-breaking space (NNBSP: "\u202F"). Additionally, when using the LONG or FULL timeStyle with dateStyle, the date and time separator has changed from ' at ' to ', '. IE. January 5, 1941, 8:00:00 AM UTC vs. January 5, 1941 at 8:00:00 AM UTC