cloudapi: add multiple upload_targets to ImageRequest

Add an upload_targets field to the image request.  This lets the API
caller specify multiple upload targets and upload options to be used.
If the upload target type does not match the upload options, the request
is invalid.

For backwards compatibility, the upload targets field is optional.  If
it is not specified, the default upload target and upload options for
the image type are assumed, which is the same as the old behaviour.

Adding an explicit selection to the request makes it possible to support
multiple upload targets for the same image type.  We plan to support
ostree commits being uploaded to both aws.s3 and pulp.

To report on the multiple upload requests, we add an upload_statuses
field to the ImageStatus response.

internal/cloudapi/v2/openapi.v2.yml

@@ -767,7 +767,20 @@ components:
             $ref: '#/components/schemas/Repository'
         ostree:
           $ref: '#/components/schemas/OSTree'
+        upload_targets:
+          type: array
+          description: |
+            The type and options for multiple upload targets. Each item defines
+            a separate upload destination with its own options. Multiple
+            different targets as well as multiple targets of the same kind are
+            supported.
+          items:
+            $ref: '#/components/schemas/UploadTarget'
         upload_options:
+          description: |
+            Top level upload options for a single upload target. If this is
+            defined, it is used with the default target type for the image type
+            and is combined with the targets defined in upload_targets.
           $ref: '#/components/schemas/UploadOptions'
         size:
           x-go-type: uint64
@@ -901,12 +914,24 @@ components:
       properties:
         selected:
           type: array
-          items: 
+          items:
             type: string
         unselected:
           type: array
-          items: 
+          items:
             type: string
+    UploadTarget:
+      type: object
+      required:
+        - type
+        - upload_options
+      properties:
+        type:
+          $ref: '#/components/schemas/UploadTypes'
+          description: |
+            The name of the upload target that matches the upload_options.
+        upload_options:
+          $ref: '#/components/schemas/UploadOptions'
     UploadOptions:
       anyOf:
       - $ref: '#/components/schemas/AWSEC2UploadOptions'
@@ -917,6 +942,7 @@ components:
       - $ref: '#/components/schemas/LocalUploadOptions'
       - $ref: '#/components/schemas/OCIUploadOptions'
       description: |
+        Options for a given upload destination.
         This should really be oneOf but AWSS3UploadOptions is a subset of
         AWSEC2UploadOptions. This means that all AWSEC2UploadOptions objects
         are also valid AWSS3UploadOptionas objects which violates the oneOf