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

import (
	"net/http"

	portainer "github.com/portainer/portainer/api"
	"github.com/portainer/portainer/api/dataservices"
	httperror "github.com/portainer/portainer/pkg/libhttp/error"
	"github.com/portainer/portainer/pkg/libhttp/request"
	"github.com/portainer/portainer/pkg/libhttp/response"

	"github.com/pkg/errors"
)

type endpointUpdateRelationsPayload struct {
	Relations map[portainer.EndpointID]struct {
		EdgeGroups []portainer.EdgeGroupID
		Tags       []portainer.TagID
		Group      portainer.EndpointGroupID
	}
}

func (payload *endpointUpdateRelationsPayload) Validate(r *http.Request) error {
	for eID := range payload.Relations {
		if eID == 0 {
			return errors.New("Missing environment identifier")
		}
	}

	return nil
}

// @id EndpointUpdateRelations
// @summary Update relations for a list of environments
// @description Update relations for a list of environments
// @description Edge groups, tags and environment group can be updated.
// @description
// @description **Access policy**: administrator
// @tags endpoints
// @security jwt
// @accept json
// @param body body endpointUpdateRelationsPayload true "Environment relations data"
// @success 204 "Success"
// @failure 400 "Invalid request"
// @failure 401 "Unauthorized"
// @failure 404 "Not found"
// @failure 500 "Server error"
// @router /endpoints/relations [put]
func (handler *Handler) updateRelations(w http.ResponseWriter, r *http.Request) *httperror.HandlerError {

	payload, err := request.GetPayload[endpointUpdateRelationsPayload](r)
	if err != nil {
		return httperror.BadRequest("Invalid request payload", err)
	}

	err = handler.DataStore.UpdateTx(func(tx dataservices.DataStoreTx) error {
		for environmentID, relationPayload := range pa
    
func (handler *Handler) updateRelations(w http.ResponseWriter, r *http.Request) *httperror.HandlerError {

	payload, err := request.GetPayload[endpointUpdateRelationsPayload](r)
	if err != nil {
		return httperror.BadRequest("Invalid request payload", err)
	}

	err = handler.DataStore.UpdateTx(func(tx dataservices.DataStoreTx) error {
		for environmentID, relationPayload := range payload.Relations {
			endpoint, err := tx.Endpoint().Endpoint(environmentID)
			if err != nil {
				return errors.WithMessage(err, "Unable to find an environment with the specified identifier inside the database")
			}

			updateRelations := false

			if relationPayload.Group != 0 {
				groupIDChanged := endpoint.GroupID != relationPayload.Group
				endpoint.GroupID = relationPayload.Group
				updateRelations = updateRelations || groupIDChanged
			}

			if relationPayload.Tags != nil {
				tagsChanged, err := updateEnvironmentTags(tx, relationPayload.Tags, endpoint.TagIDs, endpoint.ID)
				if err != nil {
					return errors.WithMessage(err, "Unable to update environment tags")
				}

				endpoint.TagIDs = relationPayload.Tags
				updateRelations = updateRelations || tagsChanged
			}

			if relationPayload.EdgeGroups != nil {
				edgeGroupsChanged, err := updateEnvironmentEdgeGroups(tx, relationPayload.EdgeGroups, endpoint.ID)
				if err != nil {
					return errors.WithMessage(err, "Unable to update environment edge groups")
				}

				updateRelations = updateRelations || edgeGroupsChanged
			}

			if updateRelations {
				err := tx.Endpoint().UpdateEndpoint(endpoint.ID, endpoint)
				if err != nil {
					return errors.WithMessage(err, "Unable to update environment")
				}

				err = handler.updateEdgeRelations(tx, endpoint)
				if err != nil {
					return errors.WithMessage(err, "Unable to update environment relations")
				}
			}
		}

		return nil
	})

	if err != nil {
		return httperror.InternalServerError("Unable to update environment relations", err)
	}

	return response.Empty(w)
}