[UII] Support integrations having secrets with multiple values

[jen-huang]

Summary

Resolves #205102. This PR makes Fleet support having multiple values for secrets, i.e. integrations with variables such as:

  - name: connection_string
    title: Connection String
    type: password
    secret: true
    multi: true

When a package policy has a multi-value secret, the variable containing references to secrets will be saved with ids: string[]:

"connection_string": {
  "type": "password",
  "value": {
    "ids": [
      "c9A385UBLd_jDJtMILH5",
      "ddA385UBLd_jDJtMILH5"
    ],
    "isSecretRef": true
  }
}

There is no change for secrets with single values, the reference will still be saved with id: string. There is also no change to the secret_references block.

The policy editor will display the multi-value secrets like this when creating:

And when editing/replacing:

Testing

1. Download and upload test package azure-1.20.5-next.zip, which modifies connection_string to be multi-value secret and updates associated agent handlebars templates

• You may get an error about integration name not found, I'm not sure what that error is, but the package will still be uploaded

2. Test adding the above version of Azure package policy with multiple connection strings
3. Check that the agent yaml compiles correctly
4. Test editing, deleting the policies etc

Checklist

• Unit or functional tests were updated or added to match the most common scenarios
• The PR description includes the appropriate Release Notes section, and the correct release_note:* label is applied per the guidelines

[elasticmachine]

Pinging @elastic/fleet (Team:Fleet)

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: 26a5591

Metrics [docs]

Page load bundle

Size of the bundles that are downloaded on every page load. Target size is below 100kb

id	before	after	diff
fleet	161.6KB	162.2KB	+577.0B

cc @jen-huang

[nchaulet]

Tested locally and it generated a correct fleet policy and associated secrets. LGTM 🚀

[bvader]

Hi @jen-huang Do I read this right that this will not be backported to 8.19? We will have enterprise customers on 8.X for many many months, any chance it can get added to the backport?