Add complete flag environment variable to agent metadata

[emilioalvap]

What does this PR do?

Closes elastic/fleet-server#1754. Add environment variable to agent complete image and add it to agent metada.

Why is it important?

We need a mechanism to detect if the agent enrolled is a -complete image in Synthetics to show early warnings which the spec does not provide.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in ./changelog/fragments using the changelog tool
• I have added an integration test or an E2E test

How to test this PR locally

1. Build agent docker images locally.
2. Enroll both an elastic-agent and elastic-agent-complete containers on a policy.
3. Check both agents metadata for complete flag:

//complete
 "local_metadata": {
    "elastic": {
        ...,
        "complete": true,
      }
    },
}
//vs non-complete
 "local_metadata": {
    "elastic": {
      "agent": {
        ...,
        "complete": false,
      }
    },
}

[mergify]

This pull request does not have a backport label. Could you fix it @emilioalvap? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-v./d./d./d is the label to automatically backport to the 8./d branch. /d is the digit

NOTE: backport-skip has been added to this pull request.

[elasticmachine]

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• Start Time: 2023-08-08T14:17:44.694+0000

• Duration: 63 min 42 sec

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Total	6240

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🤖 GitHub comments

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[mergify]

This pull request is now in conflicts. Could you fix it? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b agent-complete-local-metadata upstream/agent-complete-local-metadata
git merge upstream/main
git push upstream agent-complete-local-metadata

[elasticmachine]

🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	98.734% (78/79)	👍
Files	66.549% (189/284)	👍
Classes	65.399% (344/526)	👍
Methods	52.233% (1076/2060)	👎 -0.025
Lines	38.346% (12321/32131)	👎 -0.005
Conditionals	100.0% (0/0)	💚

[emilioalvap]

/test

[emilioalvap]

/test

[blakerouse]

When a customer reads the changelog what does this mean to them? Maybe some more information on why this is done would be better.

[blakerouse]

Should this information be added to the VersionInfo? That is the information that is exposed from the elastic-agent version command line. Is that information important to know there? Being that we want to let fleet know seems like its important. That information would then be provided in diagnostics.

[emilioalvap]

I don't think it would make sense to include it from the synthetics pov. For us, this is telling us that a given agent is running inside Docker with synthetics deps bundled. For us having ELASTIC_AGENT_COMPLETE: "true" on the diagnostics file is a direct correlation so no need to display it on the version. But I can add it if you think it'll add value

[blakerouse]

I agree that it is only for synthetics and inside of a container. How will the information that its a complete image get into the diagnostics zip archive?

[emilioalvap]

Diagnostics includes the agent environment:

env:
    BEAT_SETUID_AS: elastic-agent
    ELASTIC_AGENT_COMPLETE: "true"

[blakerouse]

Okay, sounds good.

[blakerouse]

Please update the changelog before merging, otherwise looks good!