weldr/compose: add support for ostree-specific options

Similarly to how some image types accept a size-argument, some image
types require  ostree-specific options. For now this is only used by
Fedora IoT on Fedora 32.

composer-cli nor cockpit-composer currently has the ability to pass in
these options, but the change is backwards compatible and existing image
types are unaffected. If the options are omitted for image types that
require them, sensible defaults are chosen.

Signed-off-by: Tom Gundersen <teg@jklm.no>

internal/weldr/api.go

@@ -1506,11 +1506,17 @@ func (api *API) composeHandler(writer http.ResponseWriter, request *http.Request
 		return
 	}
 
+	type OSTreeRequest struct {
+		Ref    string `json:"ref"`
+		Parent string `json:"parent"`
+	}
+
 	// https://weldr.io/lorax/pylorax.api.html#pylorax.api.v0.v0_compose_start
 	type ComposeRequest struct {
 		BlueprintName string         `json:"blueprint_name"`
 		ComposeType   string         `json:"compose_type"`
 		Size          uint64         `json:"size"`
+		OSTree        OSTreeRequest  `json:"ostree"`
 		Branch        string         `json:"branch"`
 		Upload        *uploadRequest `json:"upload"`
 	}
@@ -1606,6 +1612,10 @@ func (api *API) composeHandler(writer http.ResponseWriter, request *http.Request
 	manifest, err := imageType.Manifest(bp.Customizations,
 		distro.ImageOptions{
 			Size: size,
+			OSTree: distro.OSTreeImageOptions{
+				Ref:    cr.OSTree.Ref,
+				Parent: cr.OSTree.Parent,
+			},
 		},
 		api.allRepositories(),
 		packages,