Split RNs by product (#775)

Organizes the release notes by product instead of content type.

Adds RN 9.0.0 content.

Author: KOTungseth

deploy-manage/upgrade/orchestrator/upgrade-cloud-enterprise.md

@@ -51,7 +51,7 @@ Before starting the upgrade process, check which of the following recommendation
 
 
 * We strongly recommend that you routinely update your ECE installation to the most current version so that any bugs and security issues are fixed promptly. If you need to upgrade but are currently experiencing any issues with your platform, note that as long as ZooKeeper is running and healthy you should be able to upgrade (you can use the [get runners API](https://www.elastic.co/docs/api/doc/cloud-enterprise/operation/operation-get-runners) to easily verify the health of the runners on the [ECE allocators](../../../deploy-manage/deploy/cloud-enterprise/ece-architecture.md#ece-architecture-allocators)). That is, healthy system deployments are not required in order to perform an upgrade successfully.
-* Before upgrading to Elastic Cloud Enterprise 4.0, refer to the [lists of removals](/release-notes/breaking-changes/index.md) to find out about features and API endpoints that are no longer supported.
+* Before upgrading to Elastic Cloud Enterprise 4.0, refer to the [lists of removals](cloud://release-notes/cloud-enterprise/breaking-changes.md) to find out about features and API endpoints that are no longer supported.
 * We strongly recommend that you do not attempt to perform certain actions during the upgrade process, such as:
 
     * Creating or changing Elasticsearch clusters and Kibana instances

docset.yml

@@ -384,10 +384,16 @@ subs:
   multi-arg-ref:   "†footnoteref:[multi-arg]"
   yes-icon:   "image:https://doc-icons.s3.us-east-2.amazonaws.com/icon-yes.png[Yes,20,15]"
   no-icon:   "image:https://doc-icons.s3.us-east-2.amazonaws.com/icon-no.png[No,20,15]"
+  agent-repo:   "https://github.com/elastic/elastic-agent/"
+  agent-issue:   "https://github.com/elastic/elastic-agent/issues/"
+  agent-pull:   "https://github.com/elastic/elastic-agent/pull/"
   es-repo:   "https://github.com/elastic/elasticsearch/"
   es-issue:   "https://github.com/elastic/elasticsearch/issues/"
   es-pull:   "https://github.com/elastic/elasticsearch/pull/"
   es-commit:   "https://github.com/elastic/elasticsearch/commit/"
+  fleet-server-repo:   "https://github.com/elastic/fleet-server/"
+  fleet-server-issue:   "https://github.com/elastic/fleet-server/issues/"
+  fleet-server-pull:   "https://github.com/elastic/fleet-server/pull/"
   kib-repo:   "https://github.com/elastic/kibana/"
   kib-issue:   "https://github.com/elastic/kibana/issues/"
   kibana-issue:   "'{kib-repo}issues/'"

raw-migrated-files/stack-docs/elastic-stack/upgrading-elastic-stack.md

@@ -20,7 +20,7 @@ Upgrading from a release candidate build, such as 8.0.0-rc1 or 8.0.0-rc2, is not
     * [{{es}} migration guide](elasticsearch://release-notes/breaking-changes.md)
     * [{{elastic-sec}} release notes](https://www.elastic.co/guide/en/security/current/release-notes.html)
     * [{{ents}} release notes](https://www.elastic.co/guide/en/enterprise-search/current/changelog.html)
-    * [{{fleet}} and {{agent}} release notes](/release-notes/fleet-elastic-agent.md)
+    * [{{fleet}} and {{agent}} release notes](/release-notes/fleet-elastic-agent/release-notes.md)
     * [{{kib}} release notes](kibana://release-notes/index.md)
     * [{{ls}} breaking changes](logstash://release-notes/breaking-changes.md)
 

release-notes/breaking-changes/elastic-observability.md

@@ -3,7 +3,7 @@ navigation_title: "Elastic APM"
 ---
 
 # Elastic APM breaking changes [elastic-apm-breaking-changes]
-Before you upgrade, carefully review the Elastic APM breaking changes and take the necessary steps to mitigate any issues. 
+Breaking changes can impact your Elastic applications, potentially disrupting normal operations. Before you upgrade, carefully review the Elastic APM breaking changes and take the necessary steps to mitigate any issues. 
 
 To learn how to upgrade, check [Upgrade](/deploy-manage/upgrade.md).
 
@@ -18,7 +18,7 @@ To learn how to upgrade, check [Upgrade](/deploy-manage/upgrade.md).
 % ::::
 
 ## 9.0.0 [elastic-apm-9-0-0-breaking-changes]
-**Release date:** April 1, 2025
+**Release date:** April 2, 2025
 
 % ::::{dropdown} Title of breaking change 
 % Description of the breaking change.

release-notes/breaking-changes/fleet-elastic-agent.md

@@ -3,7 +3,9 @@ navigation_title: "Elastic APM"
 ---
 
 # Elastic APM deprecations [elastic-apm-deprecations]
-Review the deprecated functionality for your Elastic APM version. While deprecations have no immediate impact, we strongly encourage you update your implementation after you upgrade.
+Over time, certain Elastic functionality becomes outdated and is replaced or removed. To help with the transition, Elastic deprecates functionality for a period before removal, giving you time to update your applications. 
+
+Review the deprecated functionality for Elastic APM. While deprecations have no immediate impact, we strongly encourage you update your implementation after you upgrade.
 
 To learn how to upgrade, check out [Upgrade](/deploy-manage/upgrade.md).
 
@@ -18,7 +20,7 @@ To learn how to upgrade, check out [Upgrade](/deploy-manage/upgrade.md).
 % ::::
 
 % ## 9.0.0 [elastic-apm-900-deprecations]
-% **Release date:** April 1, 2025
+% **Release date:** April 2, 2025
 
 % ::::{dropdown} Deprecation title
 % Description of the deprecation.