[proposal] Move ArtifactType -> artifact.type, BuildConfig.BuildType -> build.location

[balopat]

Background

We have three places in our pipeline config where we use "inline oneOf" fields currently: BuildConfig.BuildType, DeployConfig.DeployType, Artifact.ArtifactType They are "oneOf" fields - our DIY "union types" - choices are represented as fields and we validate against multiple choices runtime. They are "inline" as these "choice fields" become part of the parent element.

e.g.:

apiVersion: skaffold/v1alpha4
kind: Config
build:
  artifacts:
  - image: gcr.io/k8s-skaffold/skaffold-example
    docker:
        target: "mytarget"
        cacheFrom:
          - "baseimage1"
          - "baseimage2"
  kaniko:
    buildContext: 
      localDir: {}
    pullSecretName: e2esecret
    namespace: default

Problem

Out of these BuildConfig.BuildType and Artifact.ArtifactType are mixed in with other properties. For example Artifact.Image, Artifact.Sync, Artifact.Context, which becomes confusing when used in an IntelliSense context:

Proposal

1.) Move ArtifactType to a non-inline field: artifact.type:

2.) Move BuildConfig.BuildType under build.location
This would also help with resolving some of the readability arguments in

#1179
#955
#953

[balopat]

After chatting with @r2d4 - this would be a deviation from the k8s pattern.

Here's the K8S API guidance for unions:
https://github.com/kubernetes/community/blob/master/contributors/devel/api-conventions.md#unions

And the example of Volume.VolumeSource fields happily mixed with the name field on Volume:
https://kubernetes.io/docs/concepts/storage/volumes#emptydir
https://github.com/kubernetes/api/blob/master/core/v1/types.go#L44

[balopat]

After some discussions within the team I'll close this. If someone feels strongly about this please reopen/comment.