worker: require workers to pass their architecture

Jobs are scheduled with type "osbuild:{arch}", to ensure that workers
only get jobs with the right architecture assigned.

internal/worker/api/api.gen.go

@@ -17,6 +17,7 @@ type Error struct {
 
 // RequestJobJSONBody defines parameters for RequestJob.
 type RequestJobJSONBody struct {
+	Arch  string   `json:"arch"`
 	Types []string `json:"types"`
 }