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: create_kubernetes_stack.go
    path of file: ./repos/portainer/api/http/handler/stacks
    
    the code of the file until where you have to start completion: package stacks

import (
	"fmt"
	"net/http"

	portainer "github.com/portainer/portainer/api"
	"github.com/portainer/portainer/api/git/update"
	"github.com/portainer/portainer/api/internal/endpointutils"
	"github.com/portainer/portainer/api/internal/registryutils"
	k "github.com/portainer/portainer/api/kubernetes"
	"github.com/portainer/portainer/api/stacks/deployments"
	"github.com/portainer/portainer/api/stacks/stackbuilders"
	"github.com/portainer/portainer/api/stacks/stackutils"
	httperror "github.com/portainer/portainer/pkg/libhttp/error"
	"github.com/portainer/portainer/pkg/libhttp/request"
	"github.com/portainer/portainer/pkg/libhttp/respons
    
func (payload *kubernetesGitDeploymentPayload) Validate(r *http.Request) error {
	if govalidator.IsNull(payload.RepositoryURL) || !govalidator.IsURL(payload.RepositoryURL) {
		return errors.New("Invalid repository URL. Must correspond to a valid URL format")
	}
	if payload.RepositoryAuthentication && govalidator.IsNull(payload.RepositoryPassword) {
		return errors.New("Invalid repository credentials. Password must be specified when authentication is enabled")
	}
	if govalidator.IsNull(payload.ManifestFile) {
		return errors.New("Invalid manifest file in repository")
	}
	if err := update.ValidateAutoUpdateSettings(payload.AutoUpdate); err != nil {
		return err
	}
	return nil
}