[9.0] Update RC1 release notes

docs/reference/migration/migrate_9_0.asciidoc

@@ -54,6 +54,21 @@ after upgrading to 9.0.
 To find out if you are using any deprecated functionality,
 enable <<deprecation-logging, deprecation logging>>.
 
+[discrete]
+[[deprecations_90_rest_api]]
+==== REST API deprecations
+
+[[add_deprecation_warning_for_flush_api]]
+.Add deprecation warning for flush API
+[%collapsible]
+====
+*Details* +
+The anomaly detection job flush API is deprecated since it is only required for the post data API, which was deprecated since 7.11.0.
+
+*Impact* +
+This should have a minimal impact on users as the flush API is only required for the post data API, which was deprecated since 7.11.0.
+====
+
 [discrete]
 [[deprecations_90_search]]
 ==== Search deprecations

docs/reference/release-notes/9.0.0.asciidoc

@@ -30,6 +30,7 @@ ES|QL::
 * Avoid over collecting in Limit or Lucene Operator {es-pull}123296[#123296]
 * Change the order of the optimization rules {es-pull}124335[#124335]
 * ESQL: Remove estimated row size assertion {es-pull}122762[#122762] (issue: {es-issue}121535[#121535])
+* ES|QL: Fix scoring for full text functions {es-pull}124540[#124540]
 * Fix early termination in `LuceneSourceOperator` {es-pull}123197[#123197]
 * Fix function registry concurrency issues on constructor {es-pull}123492[#123492] (issue: {es-issue}123430[#123430])
 * Implicit numeric casting for CASE/GREATEST/LEAST {es-pull}122601[#122601] (issue: {es-issue}121890[#121890])
@@ -50,9 +51,12 @@ Indices APIs::
 * Updates the deprecation info API to not warn about system indices and data streams {es-pull}122951[#122951]
 
 Infra/Core::
+* Fix system data streams to be restorable from a snapshot {es-pull}124651[#124651] (issue: {es-issue}89261[#89261])
 * Have create index return a bad request on poor formatting {es-pull}123761[#123761]
 * Include data streams when converting an existing resource to a system resource {es-pull}121392[#121392]
+* Prevent rare starvation bug when using scaling `EsThreadPoolExecutor` with empty core pool size. {es-pull}124732[#124732] (issue: {es-issue}124667[#124667])
 * System Index Migration Failure Results in a Non-Recoverable State {es-pull}122326[#122326]
+* System data streams are not being upgraded in the feature migration API {es-pull}124884[#124884] (issue: {es-issue}122949[#122949])
 
 Ingest Node::
 * Fix geoip databases index access after system feature migration (again) {es-pull}122938[#122938]
@@ -70,14 +74,21 @@ Machine Learning::
 
 Mapping::
 * Avoid serializing empty `_source` fields in mappings {es-pull}122606[#122606]
+* Merge template mappings properly during validation {es-pull}124784[#124784] (issue: {es-issue}123372[#123372])
+
+Ranking::
+* Fix LTR query feature with phrases (and two-phase) queries {es-pull}125103[#125103]
 
 Search::
 * Do not let `ShardBulkInferenceActionFilter` unwrap / rewrap ESExceptions {es-pull}123890[#123890]
+* Don't generate stacktrace in `TaskCancelledException` {es-pull}125002[#125002]
 * Fix concurrency issue in `ScriptSortBuilder` {es-pull}123757[#123757]
 * Handle search timeout in `SuggestPhase` {es-pull}122357[#122357] (issue: {es-issue}122186[#122186])
+* Let MLTQuery throw IAE when no analyzer is set {es-pull}124662[#124662] (issue: {es-issue}124562[#124562])
 
 Snapshot/Restore::
 * Fork post-snapshot-delete cleanup off master thread {es-pull}122731[#122731]
+* This PR fixes a bug whereby partial snapshots of system datastreams could be used to restore system features. {es-pull}124931[#124931]
 
 Suggesters::
 * Return an empty suggestion when suggest phase times out {es-pull}122575[#122575] (issue: {es-issue}122548[#122548])
@@ -92,6 +103,9 @@ Vector Search::
 [float]
 === Deprecations
 
+Machine Learning::
+* Add deprecation warning for flush API {es-pull}121667[#121667] (issue: {es-issue}121506[#121506])
+
 Search::
 * Deprecate Behavioral Analytics CRUD apis {es-pull}122960[#122960]
 
@@ -115,10 +129,17 @@ ES|QL::
 * ES|QL - Add scoring for full text functions disjunctions {es-pull}121793[#121793]
 * Fix Driver status iterations and `cpuTime` {es-pull}123290[#123290] (issue: {es-issue}122967[#122967])
 * Push down `StartsWith` and `EndsWith` functions to Lucene {es-pull}123381[#123381] (issue: {es-issue}123067[#123067])
+* Reuse child `outputSet` inside the plan where possible {es-pull}124611[#124611]
+
+Infra/CLI::
+* Ignore _JAVA_OPTIONS {es-pull}124843[#124843]
 
 Infra/Core::
 * Improve size limiting string message {es-pull}122427[#122427]
 
+Infra/REST API::
+* Indicate when errors represent timeouts {es-pull}124936[#124936]
+
 Ingest Node::
 * Allow setting the `type` in the reroute processor {es-pull}122409[#122409] (issue: {es-issue}121553[#121553])
 
@@ -129,10 +150,19 @@ Ingest Node::
 ES|QL::
 * Initial support for unmapped fields {es-pull}119886[#119886]
 
+Search::
+* Added optional parameters to QSTR ES|QL function {es-pull}121787[#121787] (issue: {es-issue}120933[#120933])
+
 [[upgrade-9.0.0]]
 [float]
 === Upgrades
 
+Infra/Core::
+* Permanently switch from Java SecurityManager to Entitlements. The Java SecurityManager has been deprecated since Java 17, and it is now completely disabled in Java 24. In order to retain an similar level of protection, Elasticsearch implemented its own protection mechanism, Entitlements. Starting with this version, Entitlements will permanently replace the Java SecurityManager. {es-pull}124865[#124865]
+
+Packaging::
+* Update bundled JDK to Java 24 {es-pull}125159[#125159]
+
 Security::
 * Bump nimbus-jose-jwt to 10.0.2 {es-pull}124544[#124544]