Implement /ext in Steve for Imperative API (#287)

This implements the Imperative API that is served at /ext with Steve. The imperative API is compatible with Kubernetes' API server and will be used as an extension API server.

pkg/ext/apiserver_suite_test.go

@@ -0,0 +1,50 @@
+package ext
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/suite"
+	"k8s.io/client-go/kubernetes"
+	"k8s.io/client-go/rest"
+	"sigs.k8s.io/controller-runtime/pkg/envtest"
+)
+
+type ExtensionAPIServerSuite struct {
+	suite.Suite
+
+	ctx    context.Context
+	cancel context.CancelFunc
+
+	testEnv    envtest.Environment
+	client     *kubernetes.Clientset
+	restConfig *rest.Config
+}
+
+func (s *ExtensionAPIServerSuite) SetupSuite() {
+	var err error
+	apiServer := &envtest.APIServer{}
+
+	s.testEnv = envtest.Environment{
+		ControlPlane: envtest.ControlPlane{
+			APIServer: apiServer,
+		},
+	}
+	s.restConfig, err = s.testEnv.Start()
+	s.Require().NoError(err)
+
+	s.client, err = kubernetes.NewForConfig(s.restConfig)
+	s.Require().NoError(err)
+
+	s.ctx, s.cancel = context.WithCancel(context.Background())
+}
+
+func (s *ExtensionAPIServerSuite) TearDownSuite() {
+	s.cancel()
+	err := s.testEnv.Stop()
+	s.Require().NoError(err)
+}
+
+func TestExtensionAPIServerSuite(t *testing.T) {
+	suite.Run(t, new(ExtensionAPIServerSuite))
+}