intake: add cloud.service.name to metadata

[simitt]

Motivation/summary

This PR adds cloud.service.name to the set of available cloud information in the metadata. The field was introduced with elastic/ecs#1204.

Checklist

• Update CHANGELOG.asciidoc
• Documentation has been updated (automatically)

For functional changes, consider:

• Is it observable through the addition of either logging or metrics?
• Is its use being published in telemetry to enable product improvement?
• Have system tests been added to avoid regression?

How to test these changes

Send a metadata.cloud.service.name information along with event data and check that it is indexed as keyword for error,transaction,span,metric events.

Related issues

closes 4625

How to add a new Intake API Field and index it

• Add the new field to the modeldecoder. In case the field should also be available for the new RUM API, also add it to the rumv3/model
• Add the new field to the model
• Add the mapping from the modeldecoder to the model
• Add the new field to the testdata and update the generated test approval files by running go test ./... and make check-approvals
• Add the field names to the meta/fields.yml where the new fields should be indexed.
• Run make update and ensure that the Intake Spec, the generated model logic and the apmpackage and the generated fields are properly updated

[apmmachine]

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Build stats

• Build Cause: Pull request #4626 updated

• • Start Time: 2021-01-25T13:52:18.229+0000

• Duration: 32 min 35 sec

• Commit: 92f6dc3

Test stats 🧪

Test	Results
Failed	0
Passed	4358
Skipped	126
Total	4484

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• Description: tar --exclude=system-tests-linux-files.tgz -czf system-tests-linux-files.tgz system-tests

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• Description: ./.ci/scripts/sync.sh

[jalvz]

Maybe add the field to docs/data/elasticsearch/generated?

Also, it would be great to create some section in the README with a link to this PR as a reference implementation of how to add a field to the intake (things have changed...)

[jalvz]

this is wrong, isn't it? I think we need to update the ECS version

[simitt]

It hasn't been released, so for now this is true.

[simitt]

@jalvz good idea; I updated the description to contain a How to add a new Intake API Field and index it section and linked to it from the updated Contribution guid.

[simitt]

When running go test -race -v ./... the TestStorageGC still fails with these changes. I don't think the PR introduces an actual bug but rather that it reveals a test issue. @axw to unblock this PR, are you ok with skipping the test for now and creating an issue to rework it?

[axw]

@simitt yes, that's fine - thanks and sorry.

[jalvz]

The go agent doesn't let you trick into thinking is running on cloud, so I just sent handcrafted payloads to apm-server. Data is ingested as expected