TT-448: add mservctl update command (#24)

While mserv supports updating bundles, the mservctl client does not currently implement this functionality. This PR implements it by adding an mservctl update command to the tool.

Usage:
mservctl update 9c9ecec1-8f98-4c3f-88cd-ca3c27599e6b bundle.zip

mservctl/cmd/update.go

@@ -0,0 +1,43 @@
+package cmd
+
+import (
+	"os"
+	"time"
+
+	"github.com/spf13/cobra"
+
+	"github.com/TykTechnologies/mserv/mservclient/client/mw"
+)
+
+// updateCmd represents the update command
+var updateCmd = &cobra.Command{
+	Use:     "update",
+	Short:   "Updates a middleware on mserv",
+	Long:    "Updates a middleware by ID",
+	Example: `mservctl update 13b0eb10-419f-40ef-838d-6d26bb2eeaa8 /path/to/bundle.zip`,
+	Args:    cobra.ExactArgs(2),
+	Run:     updateMiddleware,
+}
+
+func init() {
+	rootCmd.AddCommand(updateCmd)
+}
+
+func updateMiddleware(cmd *cobra.Command, args []string) {
+	file, err := os.Open(args[1])
+	if err != nil {
+		log.WithError(err).Error("Couldn't open the bundle file")
+		return
+	}
+	defer file.Close()
+
+	params := mw.NewMwUpdateParams().WithID(args[0]).WithUploadFile(file).WithTimeout(120 * time.Second)
+
+	resp, err := mservapi.Mw.MwUpdate(params, defaultAuth())
+	if err != nil {
+		log.WithError(err).Error("Couldn't update middleware")
+		return
+	}
+
+	cmd.Printf("Middleware uploaded successfully, ID: %s\n", resp.GetPayload().Payload.BundleID)
+}