Forward port release notes for v8.17.5 (#127024)

docs/reference/migration/index.asciidoc

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+include::migration_intro.asciidoc[]
+
+* <<migrating-9.1,Migrating to 9.1>>
+* <<migrating-9.0,Migrating to 9.0>>
+
+include::migrate_9_1.asciidoc[]
+include::migrate_9_0.asciidoc[]
+

docs/reference/migration/migrate_8_17.asciidoc

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+[[migrating-8.17]]
+== Migrating to 8.17
+++++
+<titleabbrev>8.17</titleabbrev>
+++++
+
+This section discusses the changes that you need to be aware of when migrating
+your application to {es} 8.17.
+
+See also <<release-highlights>> and <<es-release-notes>>.
+
+[discrete]
+[[breaking-changes-8.17]]
+=== Breaking changes
+
+There are no breaking changes in {es} 8.17.
+
+
+[discrete]
+[[deprecated-8.17]]
+=== Deprecations
+
+The following functionality has been deprecated in {es} 8.17
+and will be removed in a future version.
+While this won't have an immediate impact on your applications,
+we strongly encourage you to take the described steps to update your code
+after upgrading to 8.17.
+
+To find out if you are using any deprecated functionality,
+enable <<deprecation-logging, deprecation logging>>.
+
+[discrete]
+[[deprecations_817_mapping]]
+==== Mapping deprecations
+
+[[deprecate_source_mode_in_mappings]]
+.Deprecate `_source.mode` in mappings
+[%collapsible]
+====
+*Details* +
+Configuring `_source.mode` in mappings is deprecated and will be removed in future versions. Use `index.mapping.source.mode` index setting instead.
+
+*Impact* +
+Use `index.mapping.source.mode` index setting instead
+====
+
+[discrete]
+[[deprecations_817_rest_api]]
+==== REST API deprecations
+
+[[format_of_non_detailed_error_responses_changing_in_v9]]
+.The format of non-detailed error responses is changing in v9
+[%collapsible]
+====
+*Details* +
+When an error occurs when processing a request, Elasticsearch returns information on that error in the REST response.
+If `http:detailed_errors.enabled: false` is specified in node settings with the v8 REST API and below,
+the format of this response changes significantly.
+Starting with the v9 REST API, the JSON structure of responses with errors when the `http.detailed_errors.enabled: false` option is set
+will be the same as when detailed errors are enabled (which is the default).
+To keep using the existing format for non-detailed error responses, use the v8 REST API.
+
+*Impact* +
+If you have set `http.detailed_errors.enabled: false` (the default is `true`)
+the structure of JSON when any exceptions occur will change with the v9 REST API.
+To keep using the existing format, use the v8 REST API.
+====
+

docs/reference/release-notes.asciidoc

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+[[es-release-notes]]
+= Release notes
+
+[partintro]
+--
+
+This section summarizes the changes in each release.
+
+* <<release-notes-9.1.0>>
+* <<release-notes-9.0.0>>
+* <<release-notes-9.0.0-rc1>>
+* <<release-notes-9.0.0-beta1>>
+
+--
+
+include::release-notes/9.1.0.asciidoc[]
+include::release-notes/9.0.0.asciidoc[]
+include::release-notes/9.0.0-rc1.asciidoc[]
+include::release-notes/9.0.0-beta1.asciidoc[]
+

docs/reference/release-notes/8.17.5.asciidoc

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+[[release-notes-8.17.5]]
+== {es} version 8.17.5
+
+Also see <<breaking-changes-8.17,Breaking changes in 8.17>>.
+
+[[bug-8.17.5]]
+[float]
+=== Bug fixes
+
+Authentication::
+* Fix NPE for missing Content Type header in OIDC Authenticator {es-pull}126191[#126191]
+
+ES|QL::
+* Fix `ReplaceMissingFieldsWithNull` {es-pull}125764[#125764] (issues: {es-issue}126036[#126036], {es-issue}121754[#121754], {es-issue}126030[#126030])
+* Fix usage of already released null block in `ValueSourceReaderOperator` {es-pull}126411[#126411] (issue: {es-issue}125850[#125850])
+
+Machine Learning::
+* Fixing bedrock event executor terminated cache issue {es-pull}118177[#118177] (issue: {es-issue}117916[#117916])
+
+Search::
+* Re-enable parallel collection for field sorted top hits {es-pull}125916[#125916]
+* Support indices created in ESv6 and updated in ESV7 using different LuceneCodecs as archive in current version. {es-pull}125389[#125389]
+
+TLS::
+* Set `keyUsage` for generated HTTP certificates and self-signed CA {es-pull}126376[#126376] (issue: {es-issue}117769[#117769])
+
+

docs/reference/release-notes/highlights.asciidoc

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+[[release-highlights]]
+== What's new in {minor-version}
+
+coming::[{minor-version}]
+
+Here are the highlights of what's new and improved in {es} {minor-version}!
+ifeval::["{release-state}"!="unreleased"]
+For detailed information about this release, see the <<es-release-notes>> and
+<<breaking-changes>>.
+
+// Add previous release to the list
+Other versions:
+
+{ref-bare}/9.0/release-highlights.html[9.0]
+
+endif::[]
+
+// The notable-highlights tag marks entries that
+// should be featured in the Stack Installation and Upgrade Guide:
+// tag::notable-highlights[]
+// [discrete]
+// === Heading
+//
+// Description.
+// end::notable-highlights[]
+
+