Define value for all constant_keyword fields in apmpackage

[carsonip]

Motivation/summary

Define value for all constant_keyword fields in apmpackage to workaround Fleet upgrade bug. Under certain conditions, it is possible that apmpackage upgrade creates a lot of indices if constant_keyword does not have a value.

Targeting 8.12 branch because apmpackage has been moved to https://github.com/elastic/integrations/tree/main/packages/apm/data_stream on main.

Checklist

• Update CHANGELOG.asciidoc
• Update package changelog.yml (only if changes to apmpackage have been made)
• Documentation has been updated

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

• Ingest APM data, upgrade package to a version that contains the fix, and verify that DS rollover is successful and mapping contains a value for constant keyword fields.

Related issues

Closes #12159

[mergify]

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

• backport-7.17 is the label to automatically backport to the 7.17 branch.
• backport-8./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.

[mergify]

This pull request is now in conflicts. Could you fix it @carsonip? 🙏
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 constant-keyword-value upstream/constant-keyword-value
git merge upstream/main
git push upstream constant-keyword-value

[carsonip]

@simitt now that apmpackage no longer lives in apm-server repo, should I split this PR into 2 parts, 1 targeting apm-server 8.12 branch, another changing https://github.com/elastic/integrations/tree/main/packages/apm/data_stream ?

[simitt]

Yeah I fear we need to put this into both places now unfortunately.

[carsonip]

Once this is merged I'll port the change to https://github.com/elastic/integrations/tree/main/packages/apm

[bmorelli25]

run docs-build

[carsonip]

This change did not go into 8.12.1. Now the plan is to land this fix in 8.12.2.

[carsonip]

testing notes

✔️ test-plan-ok

In 8.12.2, in component template metrics-apm.transaction.1m@package:

    "metricset": {
      "properties": {
        "name": {
          "type": "constant_keyword",
          "value": "transaction"
        },
        "interval": {
          "type": "constant_keyword",
          "value": "1m"
        }
      }
    },

the value of constant keyword is now set.

[carsonip]

testing notes

Upgraded from a 8.12.1 deployment with existing data in metrics-apm.service_destination.1m-default etc to 8.12.2. Upgrade went well and data streams rolled over successfully.