feat: support service completion

Closes coop-cloud/organising#165.

cli/app/run.go

@@ -102,15 +102,24 @@ var appRunCommand = &cli.Command{
 		return nil
 	},
 	BashComplete: func(c *cli.Context) {
-		appNames, err := config.GetAppNames()
-		if err != nil {
-			logrus.Warn(err)
-		}
-		if c.NArg() > 0 {
-			return
-		}
-		for _, a := range appNames {
-			fmt.Println(a)
+		switch c.NArg() {
+		case 0:
+			appNames, err := config.GetAppNames()
+			if err != nil {
+				logrus.Warn(err)
+			}
+			for _, a := range appNames {
+				fmt.Println(a)
+			}
+		case 1:
+			appName := c.Args().First()
+			serviceNames, err := config.GetAppServiceNames(appName)
+			if err != nil {
+				logrus.Warn(err)
+			}
+			for _, s := range serviceNames {
+				fmt.Println(s)
+			}
 		}
 	},
 }