Add controller API client interface (#1467)

This PR adds an interface for controller API client, it allows us to
implement mock API client for unit testing with ease and we are
able to generate spec file without accessing the real Fission server.

pkg/fission-cli/cmd/package/package.go

@@ -45,7 +45,7 @@ import (
 // create an archive upload spec in the specs directory; otherwise
 // upload the archive using client.  noZip avoids zipping the
 // includeFiles, but is ignored if there's more than one includeFile.
-func CreateArchive(client *client.Client, includeFiles []string, noZip bool, insecure bool, checksum string, specDir string, specFile string) (*fv1.Archive, error) {
+func CreateArchive(client client.Interface, includeFiles []string, noZip bool, insecure bool, checksum string, specDir string, specFile string) (*fv1.Archive, error) {
 	// get root dir
 	var rootDir string
 	var err error
@@ -241,8 +241,8 @@ func archiveName(givenNameHint string, includedFiles []string) string {
 	return fmt.Sprintf("%v-%v", util.KubifyName(includedFiles[0]), uniuri.NewLen(4))
 }
 
-func GetFunctionsByPackage(client *client.Client, pkgName, pkgNamespace string) ([]fv1.Function, error) {
-	fnList, err := client.FunctionList(pkgNamespace)
+func GetFunctionsByPackage(client client.Interface, pkgName, pkgNamespace string) ([]fv1.Function, error) {
+	fnList, err := client.V1().Function().List(pkgNamespace)
 	if err != nil {
 		return nil, err
 	}