config/v1/types_infrastructure: Add AWS Region

The image registry needs this so it can figure out where to create an
S3 bucket for installs with cluster-provisioned infrastructure [1].
We need the registry to be happy after:

  $ openshift-install create cluster

so we don't want to rely on the installer pushing this config in as a
day-2 operation.  You can extract "what AWS region am I in?" from the
cloud provider, but the registry operator is not authorized to do so.
With this addition, we provide a way for the cluster creator to
declare a default region for new infrastructure.

This field is in Status and not Spec, because we're not going to
support transitioning clusters between regions by reconciling this.
The cluster admin can write it once (in the manifest that goes up with
the bootstrap Ignition config), and then it's read-only reality
forever.

I'd prefer an +optional Region property, because you only need to set
it if you want the cluster to provision resources for you.  For
user-provided infrastructure flows, you could leave this unset.
However, the registry needs the region for its S3 client [2], even if
it's just to manage data in a user-provided bucket.  So folks who
leave the property off will have an Available:false registry until
they set region or regionEndpoint via the
configs.imageregistry.operator.openshift.io custom resource [3,4].
But Adam wanted it required [5], and going from required -> optional
later is a non-breaking change while optional -> required would be
breaking, so it's required with this commit.

I've pushed the type specifier down into platformStatus, deprecating
the old property, because discriminator fields need to live inside the
struct whose properties they discriminate [6].  It would be nice to be
able to drop the old type property and rename platformStatus to
platform, but it's too close to API freeze to be able to do that, so
we're stuck with the old name.  We'll drop the old type in v2, if we
ever have a v2 of this type.

[1]: https://github.com/openshift/cluster-image-registry-operator/blob/670539cda460d97e0a3e23f077fdf9dd00d2ccdc/pkg/clusterconfig/clusterconfig.go#L44
[2]: https://github.com/openshift/cluster-image-registry-operator/blob/670539cda460d97e0a3e23f077fdf9dd00d2ccdc/pkg/storage/s3/s3.go#L53-L65
[3]: https://github.com/openshift/cluster-image-registry-operator/blob/670539cda460d97e0a3e23f077fdf9dd00d2ccdc/manifests/00-crd.yaml
[4]: https://github.com/openshift/cluster-image-registry-operator/blob/670539cda460d97e0a3e23f077fdf9dd00d2ccdc/pkg/apis/imageregistry/v1/types.go#L179-L184
[5]: #300 (comment)
[6]: #300 (comment)

Author: wking

config/v1/types_infrastructure.go

@@ -37,16 +37,16 @@ type InfrastructureStatus struct {
 	// alphanumeric or hyphen characters.
 	InfrastructureName string `json:"infrastructureName"`
 
-	// platform is the underlying infrastructure provider for the cluster. This
-	// value controls whether infrastructure automation such as service load
-	// balancers, dynamic volume provisioning, machine creation and deletion, and
-	// other integrations are enabled. If None, no infrastructure automation is
-	// enabled. Allowed values are "AWS", "Azure", "BareMetal", "GCP", "Libvirt",
-	// "OpenStack", "VSphere", and "None". Individual components may not support
-	// all platforms, and must handle unrecognized platforms as None if they do
-	// not support that platform.
+	// platform is the underlying infrastructure provider for the cluster.
+	//
+	// Deprecated: Use platformStatus.type instead.
 	Platform PlatformType `json:"platform,omitempty"`
 
+	// platformStatus holds status information specific to the underlying
+	// infrastructure provider.
+	// +optional
+	PlatformStatus *PlatformStatus `json:"platformStatus,omitempty"`
+
 	// etcdDiscoveryDomain is the domain used to fetch the SRV records for discovering
 	// etcd servers and clients.
 	// For more info: https://github.com/etcd-io/etcd/blob/329be66e8b3f9e2e6af83c123ff89297e49ebd15/Documentation/op-guide/clustering.md#dns-discovery
@@ -93,6 +93,31 @@ const (
 	VSpherePlatformType PlatformType = "VSphere"
 )
 
+// PlatformStatus holds the current status specific to the underlying infrastructure provider
+// of the current cluster. Since these are used at status-level for the underlying cluster, it
+// is supposed that only one of the status structs is set.
+type PlatformStatus struct {
+	// type is the underlying infrastructure provider for the cluster. This
+	// value controls whether infrastructure automation such as service load
+	// balancers, dynamic volume provisioning, machine creation and deletion, and
+	// other integrations are enabled. If None, no infrastructure automation is
+	// enabled. Allowed values are "AWS", "Azure", "BareMetal", "GCP", "Libvirt",
+	// "OpenStack", "VSphere", and "None". Individual components may not support
+	// all platforms, and must handle unrecognized platforms as None if they do
+	// not support that platform.
+	Type PlatformType `json:"type"`
+
+	// AWS contains settings specific to the Amazon Web Services infrastructure provider.
+	// +optional
+	AWS *AWSPlatformStatus `json:"aws,omitempty"`
+}
+
+// AWSPlatformStatus holds the current status of the Amazon Web Services infrastructure provider.
+type AWSPlatformStatus struct {
+	// region holds the default AWS region for new AWS resources created by the cluster.
+	Region string `json:"region"`
+}
+
 // +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object
 
 // InfrastructureList is