Allow setting ES api key via env variable in container mode (#5536)

Also remove defaults for username and password set this way.

_meta/config/elastic-agent.docker.yml.tmpl

@@ -5,8 +5,9 @@ outputs:
   default:
     type: elasticsearch
     hosts: '${ELASTICSEARCH_HOSTS:http://elasticsearch:9200}'
-    username: '${ELASTICSEARCH_USERNAME:elastic}'
-    password: '${ELASTICSEARCH_PASSWORD:changeme}'
+    username: '${ELASTICSEARCH_USERNAME:}'
+    password: '${ELASTICSEARCH_PASSWORD:}'
+    api_key: '${ELASTICSEARCH_API_KEY:}'
     preset: balanced
 
 inputs:

changelog/fragments/1726144746-container-default-credentials.yaml

@@ -0,0 +1,32 @@
+# Kind can be one of:
+# - breaking-change: a change to previously-documented behavior
+# - deprecation: functionality that is being removed in a later release
+# - bug-fix: fixes a problem in a previous version
+# - enhancement: extends functionality but does not break or fix existing behavior
+# - feature: new functionality
+# - known-issue: problems that we are aware of in a given version
+# - security: impacts on the security of a product or a user’s deployment.
+# - upgrade: important information for someone upgrading from a prior version
+# - other: does not fit into any of the other categories
+kind: breaking-change
+
+# Change summary; a 80ish characters long description of the change.
+summary: Remove default credentials when running Elastic Agent in container mode
+
+# Long description; in case the summary is not enough to describe the change
+# this field accommodate a description without length limits.
+# NOTE: This field will be rendered only for breaking-change and known-issue kinds at the moment.
+description: ELASTICSEARCH_USERNAME and ELASTICSEARCH_PASSWORD now need to be explicitly set when running the agent in container mode
+
+# Affected component; usually one of "elastic-agent", "fleet-server", "filebeat", "metricbeat", "auditbeat", "all", etc.
+component: elastic-agent
+
+# PR URL; optional; the PR number that added the changeset.
+# If not present is automatically filled by the tooling finding the PR where this changelog fragment has been added.
+# NOTE: the tooling supports backports, so it's able to fill the original PR number instead of the backport PR number.
+# Please provide it if you are adding a fragment for a different PR.
+#pr: https://github.com/owner/repo/1234
+
+# Issue URL; optional; the GitHub issue related to this changeset (either closes or is part of).
+# If not present is automatically filled by the tooling with the issue linked to the PR number.
+#issue: https://github.com/owner/repo/1234

changelog/fragments/1726145045-container-api-key.yaml

@@ -0,0 +1,32 @@
+# Kind can be one of:
+# - breaking-change: a change to previously-documented behavior
+# - deprecation: functionality that is being removed in a later release
+# - bug-fix: fixes a problem in a previous version
+# - enhancement: extends functionality but does not break or fix existing behavior
+# - feature: new functionality
+# - known-issue: problems that we are aware of in a given version
+# - security: impacts on the security of a product or a user’s deployment.
+# - upgrade: important information for someone upgrading from a prior version
+# - other: does not fit into any of the other categories
+kind: enhancement
+
+# Change summary; a 80ish characters long description of the change.
+summary: Support ELASTICSEARCH_API_KEY environment variable when running in container mode
+
+# Long description; in case the summary is not enough to describe the change
+# this field accommodate a description without length limits.
+# NOTE: This field will be rendered only for breaking-change and known-issue kinds at the moment.
+#description:
+
+# Affected component; usually one of "elastic-agent", "fleet-server", "filebeat", "metricbeat", "auditbeat", "all", etc.
+component: elastic-agent
+
+# PR URL; optional; the PR number that added the changeset.
+# If not present is automatically filled by the tooling finding the PR where this changelog fragment has been added.
+# NOTE: the tooling supports backports, so it's able to fill the original PR number instead of the backport PR number.
+# Please provide it if you are adding a fragment for a different PR.
+#pr: https://github.com/owner/repo/1234
+
+# Issue URL; optional; the GitHub issue related to this changeset (either closes or is part of).
+# If not present is automatically filled by the tooling with the issue linked to the PR number.
+#issue: https://github.com/owner/repo/1234

elastic-agent.docker.yml

@@ -5,8 +5,9 @@ outputs:
   default:
     type: elasticsearch
     hosts: '${ELASTICSEARCH_HOSTS:http://elasticsearch:9200}'
-    username: '${ELASTICSEARCH_USERNAME:elastic}'
-    password: '${ELASTICSEARCH_PASSWORD:changeme}'
+    username: '${ELASTICSEARCH_USERNAME:}'
+    password: '${ELASTICSEARCH_PASSWORD:}'
+    api_key: '${ELASTICSEARCH_API_KEY:}'
     preset: balanced
 
 inputs: