docs: remove experimental label from API Key auth (#5091)

(cherry picked from commit 667e03d)

# Conflicts:
#	changelogs/head.asciidoc

_meta/beat.yml

@@ -107,7 +107,6 @@ apm-server:
   # Enable API key authorization by setting enabled to true. By default API key support is disabled.
   # Agents include a valid API key in the following format: Authorization: ApiKey <token>.
   # The key must be the base64 encoded representation of the API key's "id:key".
-  # This is an experimental feature, use with care.
   #api_key:
     #enabled: false
 

apm-server.docker.yml

@@ -107,7 +107,6 @@ apm-server:
   # Enable API key authorization by setting enabled to true. By default API key support is disabled.
   # Agents include a valid API key in the following format: Authorization: ApiKey <token>.
   # The key must be the base64 encoded representation of the API key's "id:key".
-  # This is an experimental feature, use with care.
   #api_key:
     #enabled: false
 

apm-server.yml

@@ -107,7 +107,6 @@ apm-server:
   # Enable API key authorization by setting enabled to true. By default API key support is disabled.
   # Agents include a valid API key in the following format: Authorization: ApiKey <token>.
   # The key must be the base64 encoded representation of the API key's "id:key".
-  # This is an experimental feature, use with care.
   #api_key:
     #enabled: false
 

changelogs/head.asciidoc

@@ -0,0 +1,43 @@
+[[release-notes-head]]
+== APM Server version HEAD
+
+https://github.com/elastic/apm-server/compare/7.12\...master[View commits]
+
+[float]
+==== Breaking Changes
+
+[float]
+==== Bug fixes
+* Fix `setup.template` config merging {pull}4950[4950]
+* The server now responds with 503 instead of 401 when failure is unrelated to API Key validity, e.g. if Elasticsearch is inaccessible {pull}5053[5053]
+
+[float]
+==== Intake API Changes
+
+[float]
+==== Added
+* Add support for Node.js wall time profiles {pull}4728[4728]
+* Add metricset.name field to metric docs {pull}4857[4857]
+* Add `apm-server.default_service_environment` config {pull}4861[4861]
+* Transaction histogram metrics are now recorded by default {pull}4882[4882]
+* Add `error.grouping_name` field to speed up error grouping aggregations {pull}4886[4886]
+* Add support for OpenTelemetry exception span events {pull}4876[4876]
+* Set metricset.name for breakdown metrics {pull}4910[4910]
+* Set log and http responses for server timeout {pull}4918[4918]
+* Define ES fields for cgroup.cpu and cgroup.cpuacct metrics {pull}4956[4956]
+* Log gRPC tracing requests {pull}4934[4934]
+* Improved coverage of translation of OpenTelemetry resource conventions {pull}4955[4955]
+* Set `client.ip` for events from the Elastic APM iOS agent {pull}4975[4975]
+* Calculate service destination metrics for OpenTelemetry spans {pull}4976[4976]
+* Add exponential retries to api key and tail sampling requests{pull}4991[4991]
+* Add `apm-server.rum.allow_service_names` config {pull}5030[5030]
+* Ingest pipeline for translating OpenTelemetry Java metrics to Elastic APM fields {pull}4986[4986]
+* Set `event.ingested` first in the ingest pipeline {pull}5048[5048]
+* The server now responds with a reason for some 401 Unauthorized requests {pull}5053[5053]
+* Add `session.id` and `session.sequence` fields for RUM session tracking {pull}5056[5056]
+* Support for ingesting `user.domain` {pull}5067[5067]
+* Add `"application": "apm"` metadata to API Keys created with `apm-server apikey create` {pull}5090[5090]
+* API Key auth is no longer considered experimental {pull}5091[5091]
+
+[float]
+==== Deprecated

docs/secure-communication-agents.asciidoc

@@ -30,8 +30,6 @@ include::./ssl-input.asciidoc[]
 [[api-key]]
 === API keys
 
-experimental::[]
-
 You can configure API keys to authorize requests to the APM Server.
 
 NOTE: API keys are sent as plain-text,