Add configuration to support running WAL-E.

- Set WAL_S3_BUCKET to point WAL-E where to fetch/store WAL files
- Set annotations/iam.amazonaws.com/role to set the role to access AWS"

The new env vairables are PGOP_WAL_S3_BUCKET and PGOP_KUBE_IAM_ROLE.

pkg/util/constants/constants.go

@@ -10,5 +10,6 @@ const (
 	PasswordLength           = 64
 	UserSecretTemplate       = "%s.%s.credentials.%s.%s" // Username, ClusterName, TPRName, TPRVendor
 	ZalandoDnsNameAnnotation = "zalando.org/dnsname"
+	KubeIAmAnnotation 		 = "iam.amazonaws.com/role"
 	ResourceName             = TPRName + "s"
 )