Add String method to audit.Backend interface

staging/src/k8s.io/apiserver/pkg/audit/types.go

@@ -39,4 +39,7 @@ type Backend interface {
 	// events are delivered. It can be assumed that this method is called after
 	// the stopCh channel passed to the Run method has been closed.
 	Shutdown()
+
+	// Returns the backend PluginName.
+	String() string
 }

staging/src/k8s.io/apiserver/pkg/audit/union_test.go

@@ -40,6 +40,10 @@ func (f *fakeBackend) Shutdown() {
 	// Nothing to do here.
 }
 
+func (f *fakeBackend) String() string {
+	return ""
+}
+
 func TestUnion(t *testing.T) {
 	backends := []Backend{
 		new(fakeBackend),

staging/src/k8s.io/apiserver/plugin/pkg/audit/fake/fake.go

@@ -44,3 +44,7 @@ func (b *Backend) ProcessEvents(ev ...*auditinternal.Event) {
 		b.OnRequest(ev)
 	}
 }
+
+func (b *Backend) String() string {
+	return ""
+}

test/integration/examples/webhook_test.go

@@ -111,8 +111,14 @@ type auditSinkFunc func(events ...*auditinternal.Event)
 func (f auditSinkFunc) ProcessEvents(events ...*auditinternal.Event) {
 	f(events...)
 }
+
 func (auditSinkFunc) Run(stopCh <-chan struct{}) error {
 	return nil
 }
+
 func (auditSinkFunc) Shutdown() {
 }
+
+func (auditSinkFunc) String() string {
+	return ""
+}