Move to using templates-sdk repo for http function

[alexellis]

Signed-off-by: Alex Ellis (OpenFaaS Ltd) alexellis2@gmail.com

Description

Move to using templates-sdk repo for http function

The HTTP function now makes use of a dedicated repository
for SDK resources in the openfaas org.

How Has This Been Tested?

e2e testing with a newly created function on my kind cluster, then I changed the code and ran faas up to see the change reflect.

package function

import (
	"fmt"
	"net/http"

	handler "github.com/openfaas/templates-sdk/go-http"
)

// Handle a function invocation
func Handle(req handler.Request) (handler.Response, error) {
	var err error

	message := fmt.Sprintf("hallo alex, input was: %s", string(req.Body))

	return handler.Response{
		Body:       []byte(message),
		StatusCode: http.StatusOK,
	}, err
}

How are existing users impacted? What migration steps/scripts do we need?

I don't believe that they are affected, the previous repo still exists that held the go function SDK, but is archived.