Registry tool: should `registry apply` merge fields?

[timburks]

A user suggested that it would be helpful if registry apply could merge values in artifacts. For example, after the following two files were applied, there would be a single artifact with both team and email fields set. Currently each apply fully replaces an existing artifact.

apiVersion: apigeeregistry/v1
kind: FieldSet
metadata:
  parent: apis/sample
  name: support
data:
  definitionName: projects/PROJECTID/locations/global/artifacts/support
  values:
    team: "Team"

apiVersion: apigeeregistry/v1
kind: FieldSet
metadata:
  parent: apis/sample
  name: support
data:
  definitionName: projects/PROJECTID/locations/global/artifacts/support
  values:
    email: "apiteam@acme.com"