Resolve "Implement missing functionality of subscription management"

Description

Related Issue

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

Related to #385

cli/cmd/subManagementAdd.go

@@ -46,10 +46,10 @@ var subAddCmd = &cobra.Command{
 	Run: func(cmd *cobra.Command, args []string) {
 		spinner, _ := pterm.DefaultSpinner.Start("Adding subscription")
 
-		// TODO: add option to provide sub options??
+		// Note: Currently, doesn't support providing options/paths.
 		_, err := api.Add(createContextWithAuthorization(), viper.GetString("controllerAPIEndpoint"), mneUUID, nil)
 		if err != nil {
-			pterm.Error.Println(err)
+			spinner.Fail(err)
 			return
 		}
 		spinner.Success()