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/list.go

@@ -25,28 +25,20 @@ import (
 
 	"github.com/pkg/errors"
 
-	"github.com/fission/fission/pkg/controller/client"
 	"github.com/fission/fission/pkg/fission-cli/cliwrapper/cli"
+	"github.com/fission/fission/pkg/fission-cli/cmd"
 	flagkey "github.com/fission/fission/pkg/fission-cli/flag/key"
-	"github.com/fission/fission/pkg/fission-cli/util"
 )
 
 type ListSubCommand struct {
-	client       *client.Client
+	cmd.CommandActioner
 	listOrphans  bool
 	status       string
 	pkgNamespace string
 }
 
 func List(input cli.Input) error {
-	c, err := util.GetServer(input)
-	if err != nil {
-		return err
-	}
-	opts := ListSubCommand{
-		client: c,
-	}
-	return opts.do(input)
+	return (&ListSubCommand{}).do(input)
 }
 
 func (opts *ListSubCommand) do(input cli.Input) error {
@@ -66,7 +58,7 @@ func (opts *ListSubCommand) complete(input cli.Input) error {
 }
 
 func (opts *ListSubCommand) run(input cli.Input) error {
-	pkgList, err := opts.client.PackageList(opts.pkgNamespace)
+	pkgList, err := opts.Client().V1().Package().List(opts.pkgNamespace)
 	if err != nil {
 		return err
 	}
@@ -83,7 +75,7 @@ func (opts *ListSubCommand) run(input cli.Input) error {
 		show := true
 		// TODO improve list speed when --orphan
 		if opts.listOrphans {
-			fnList, err := GetFunctionsByPackage(opts.client, pkg.Metadata.Name, pkg.Metadata.Namespace)
+			fnList, err := GetFunctionsByPackage(opts.Client(), pkg.Metadata.Name, pkg.Metadata.Namespace)
 			if err != nil {
 				return errors.Wrap(err, fmt.Sprintf("get functions sharing package %s", pkg.Metadata.Name))
 			}