You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: signedinuser.go
    path of file: ./repos/grafana/pkg/services/apiserver/auth/authenticator
    
    the code of the file until where you have to start completion: package authenticator

import (
	"net/http"
	"strconv"

	"k8s.io/apiserver/pkg/authentication/authenticator"
	k8suser "k8s.io/apiserver/pkg/authentication/user"
	"k8s.io/klog/v2"

	"github.com/grafana/grafana/pkg/infra/appcontext"
)

var _ authenticator.RequestFunc = signedInUserAuthenticator

func signedInUserAuthenticator(req *http.Request) (*authenticator.Response, bool, error) {
	ctx := req.Context()
	signedInUser, err := appcontext.User(ctx)
	if err != nil {
		klog.V(5).Info("failed to get signed in user", "err", err)
		return nil, false, nil
	}

	userInfo := &k8suser.DefaultInfo{
		Name:   signedInUser.Login,
		UID:    signedInUser.UserUID,
		Groups: []string{},
		// In order to faithfully round-trip through an impersonation flow, Extra
    
func signedInUserAuthenticator(req *http.Request) (*authenticator.Response, bool, error) {
	ctx := req.Context()
	signedInUser, err := appcontext.User(ctx)
	if err != nil {
		klog.V(5).Info("failed to get signed in user", "err", err)
		return nil, false, nil
	}

	userInfo := &k8suser.DefaultInfo{
		Name:   signedInUser.Login,
		UID:    signedInUser.UserUID,
		Groups: []string{},
		// In order to faithfully round-trip through an impersonation flow, Extra keys MUST be lowercase.
		// see: https://pkg.go.dev/k8s.io/apiserver@v0.27.1/pkg/authentication/user#Info
		Extra: map[string][]string{},
	}

	for _, v := range signedInUser.Teams {
		userInfo.Groups = append(userInfo.Groups, strconv.FormatInt(v, 10))
	}

	//
	if signedInUser.IDToken != "" {
		userInfo.Extra["id-token"] = []string{signedInUser.IDToken}
	}

	return &authenticator.Response{
		User: userInfo,
	}, true, nil
}