refactor: centralise app name validation

cli/app/config.go

@@ -1,7 +1,6 @@
 package app
 
 import (
-	"errors"
 	"os"
 	"os/exec"
 
@@ -17,10 +16,7 @@ var appConfigCommand = &cli.Command{
 	Aliases: []string{"c"},
 	Usage:   "Edit app config",
 	Action: func(c *cli.Context) error {
-		appName := c.Args().First()
-		if appName == "" {
-			internal.ShowSubcommandHelpAndError(c, errors.New("no app name provided"))
-		}
+		appName := internal.ValidateAppNameArg(c)
 
 		appFiles, err := config.LoadAppFiles("")
 		if err != nil {