global artifacts rollout channel

[intxgo]

Change Summary

Global artifacts are going to be rolled out gradually, only a selected few endpoints will receive the fast update. This PR adds global artifacts channel field which will indicate which artifacts were currently used by the Endpoint.

Sample values

Endpoint using standard stable artifacts:
"Endpoint.policy.applied.artifacts.global.channel": "stable"

Endpoint testing artifacts from rapid rollout channel:
"Endpoint.policy.applied.artifacts.global.channel": "rapid"

Sample document:

Endpoint altert and Endpoint policy response:

{
    "Endpoint": {
        "policy": {
            "applied": {
                "artifacts": {
                    "global": {
                        "channel": "stable,
                    },
}

Release Target

Q/A

For mapping changes:

• I ran make after making the schema changes, and committed all changes
• If these field(s) are "exception"-able, I made a companion PR to Kibana adding it (see Readme)
• If this is a metadata change, I also updated both transform destination schemas to match

For Transform changes:

• The new transform successfully starts in Kibana
• The corresponding transform destination schema was updated if necessary

[nicholasberlin]

LGTM, thanks for the clean up