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: get_env_group_all_versions.go
    path of file: ./repos/porter/api/server/handlers/namespace
    
    the code of the file until where you have to start completion: package namespace

import (
	"errors"
	"fmt"
	"net/http"

	"github.com/porter-dev/porter/api/server/authz"
	"github.com/porter-dev/porter/api/server/handlers"
	"github.com/porter-dev/porter/api/server/shared"
	"github.com/porter-dev/porter/api/server/shared/apierrors"
	"github.com/porter-dev/porter/api/server/shared/config"
	"github.com/porter-dev/porter/api/types"
	"github.com/porter-dev/porter/internal/kubernetes"
	"github.com/porter-dev/porter/internal/kubernetes/envgroup"
	"github.com/porter-dev/porter/internal/models"
)

type GetEnvGroupAllVersionsHandler struct {
	handlers.PorterHandlerReadWriter
	authz.KubernetesAgentGetter
}

func NewGetEnvGroupAllVersionsHandler(
	config *config.Config,
	decoderValidator shar
    
func (c *GetEnvGroupAllVersionsHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	request := &types.GetEnvGroupAllRequest{}

	if ok := c.DecodeAndValidate(w, r, request); !ok {
		return
	}

	namespace := r.Context().Value(types.NamespaceScope).(string)
	cluster, _ := r.Context().Value(types.ClusterScope).(*models.Cluster)

	agent, err := c.GetAgent(r, cluster, "")
	if err != nil {
		c.HandleAPIError(w, r, apierrors.NewErrInternal(err))
		return
	}

	configMaps, err := agent.ListVersionedConfigMaps(request.Name, namespace)

	if err != nil && errors.Is(err, kubernetes.IsNotFoundError) {
		c.HandleAPIError(w, r, apierrors.NewErrPassThroughToClient(
			fmt.Errorf("env group not found"),
			http.StatusNotFound,
		))
		return
	} else if err != nil {
		c.HandleAPIError(w, r, apierrors.NewErrInternal(err))
		return
	}

	res := make(types.ListEnvGroupsResponse, 0)

	for _, cm := range configMaps {
		eg, err := envgroup.ToEnvGroup(&cm)
		if err != nil {
			continue
		}

		res = append(res, &types.EnvGroupMeta{
			Name:      eg.Name,
			Namespace: eg.Namespace,
			Version:   eg.Version,
		})
	}

	c.WriteResult(w, r, res)
}