refactor: separate workload class from placement driver

internal/podbackend/backend.go

@@ -120,7 +120,7 @@ func (b Backend) RecoverAssignments(ctx context.Context) ([]taskassignment.Assig
 	if err := b.validate(); err != nil {
 		return nil, err
 	}
-	pods, err := b.API.ListPods(ctx, b.Config.Namespace, "ci.ddupan.top/backend=pod")
+	pods, err := b.API.ListPods(ctx, b.Config.Namespace, "ci.ddupan.top/workload-class=container,ci.ddupan.top/driver=kubernetes")
 	if err != nil {
 		return nil, fmt.Errorf("list recoverable assignment Pods: %w", err)
 	}
@@ -159,8 +159,8 @@ func (b Backend) Create(ctx context.Context, assignment taskassignment.Assignmen
 	if err := b.validate(); err != nil {
 		return nil, err
 	}
-	if assignment.Backend != taskassignment.BackendPod {
-		return nil, fmt.Errorf("Pod backend cannot create %q assignment", assignment.Backend)
+	if assignment.Placement != taskassignment.KubernetesContainer {
+		return nil, fmt.Errorf("Kubernetes backend cannot create %q", assignment.Placement.Key())
 	}
 	labels := clone(launch.Metadata.Labels)
 	labels["app.kubernetes.io/name"] = "gitea-dynamic-runner"

internal/podbackend/backend_test.go

@@ -59,7 +59,7 @@ func backend(api API) Backend {
 
 func assignment() taskassignment.Assignment {
 	return taskassignment.Assignment{
-		ID: "gitea-task-42", Backend: taskassignment.BackendPod,
+		ID: "gitea-task-42", Placement: taskassignment.KubernetesContainer,
 		Task: &runnerv1.Task{Id: 42},
 		Identity: taskidentity.Identity{
 			Repository: "owner/repo", Task: "publish",