K8s: Add subresource to the example apiserver (#78030)

pkg/registry/apis/example/subresource.go

@@ -0,0 +1,54 @@
+package example
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apiserver/pkg/registry/rest"
+
+	example "github.com/grafana/grafana/pkg/apis/example/v0alpha1"
+	"github.com/grafana/grafana/pkg/infra/appcontext"
+	"github.com/grafana/grafana/pkg/services/grafana-apiserver/endpoints/request"
+)
+
+type dummySubresourceREST struct{}
+
+var _ = rest.Connecter(&dummySubresourceREST{})
+
+func (r *dummySubresourceREST) New() runtime.Object {
+	return &example.DummySubresource{}
+}
+
+func (r *dummySubresourceREST) Destroy() {
+}
+
+func (r *dummySubresourceREST) ConnectMethods() []string {
+	return []string{"GET"}
+}
+
+func (r *dummySubresourceREST) NewConnectOptions() (runtime.Object, bool, string) {
+	return nil, false, "" // true means you can use the trailing path as a variable
+}
+
+func (r *dummySubresourceREST) Connect(ctx context.Context, name string, opts runtime.Object, responder rest.Responder) (http.Handler, error) {
+	info, err := request.NamespaceInfoFrom(ctx, true)
+	if err != nil {
+		return nil, err
+	}
+
+	user, err := appcontext.User(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	// This response object format is negotiated by k8s
+	dummy := &example.DummySubresource{
+		Info: fmt.Sprintf("%s/%s", info.Value, user.Login),
+	}
+
+	return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+		responder.Object(http.StatusOK, dummy)
+	}), nil
+}