Doc: Add Fleet Server and Elastic Agent release notes for 8.19.4 (#1854)

Author: karenzone

docs/en/ingest-management/release-notes/release-notes-8.19.asciidoc

@@ -14,6 +14,7 @@
 
 This section summarizes the changes in each release.
 
+* <<release-notes-8.19.4>>
 * <<release-notes-8.19.3>>
 * <<release-notes-8.19.2>>
 * <<release-notes-8.19.1>>
@@ -24,6 +25,43 @@ Also see:
 * {kibana-ref}/release-notes.html[{kib} release notes]
 * {beats-ref}/release-notes.html[{beats} release notes]
 
+// begin 8.19.4 relnotes
+
+[[release-notes-8.19.4]]
+== {fleet} and {agent} 8.19.4
+
+[discrete]
+[[features-enhancements-8.19.4]]
+=== New features and enhancements
+
+Elastic Agent::
+* Bump kube-stack Helm Chart to 0.9.1 and enable the cluster collector. link:https://github.com/elastic/elastic-agent/pull/9535[#9535] 
+* Enhanced loggers for easier debugging of upgrade related issues. link:https://github.com/elastic/elastic-agent/pull/9689[#9689] link:https://github.com/elastic/elastic-agent/issues/9536[#9536]
+
+
+[discrete]
+[[bug-fixes-8.19.4]]
+=== Bug fixes
+
+Elastic Agent::
+* Redact secrets from pre-config, computed-config, components-expected, and components-actual files in diagnostics archive. link:https://github.com/elastic/elastic-agent/pull/9560[#9560] 
+* Retry service start command upon failure with 30-second delay. link:https://github.com/elastic/elastic-agent/pull/9313[#9313] 
+* Fix reporting of scheduled upgrade details across restarts and cancels. link:https://github.com/elastic/elastic-agent/pull/9562[#9562] link:https://github.com/elastic/elastic-agent/issues/8778[#8778]
+* Enable root user to re-enroll unprivileged agent for mac and linux. link:https://github.com/elastic/elastic-agent/pull/9603[#9603] link:https://github.com/elastic/elastic-agent/issues/8544[#8544]
+* Fix missing liveness healthcheck during container enrollment. link:https://github.com/elastic/elastic-agent/pull/9612[#9612] link:https://github.com/elastic/elastic-agent/issues/9611[#9611]
+* Enable admin user to re-enroll unprivileged agent for windows. link:https://github.com/elastic/elastic-agent/pull/9623[#9623] link:https://github.com/elastic/elastic-agent/issues/8544[#8544]
+* Treat exit code 284 from Endpoint binary as non-fatal. link:https://github.com/elastic/elastic-agent/pull/9687[#9687] 
+* Ensure failed upgrade actions are removed from queue and details are set. link:https://github.com/elastic/elastic-agent/pull/9634[#9634] link:https://github.com/elastic/elastic-agent/issues/9629[#9629]
+
+
+Fleet Server::
+* Restore connection limiter. link:https://github.com/elastic/fleet-server/pull/5372[#5372]
++
+Restore connection level limiter to prevent OOM incidents. This limiter is used in addition to the request-level throttle so that once our in-flight requests reaches max_connections a 429 is returned, but if the total connections the server uses is over max_connections*1.1 the server dropsthe connection before the TLS handshake.
+* Build fleet-server as fully static binary to restore OS matrix compatibility. link:https://github.com/elastic/fleet-server/pull/5392[#5392] link:https://github.com/elastic/fleet-server/issues/5262[#5262]
+ 
+// end 8.19.4 relnotes
+
 // begin 8.19.3 relnotes
 
 [[release-notes-8.19.3]]