Refactor astartectl utils interfaces, triggers

Add validation confirmation messages for Astarte Interface and Trigger

Signed-off-by: Osman Hadzic <osman.hadzic@secomind.com>

Author: osmanhadzic

cmd/utils/interfaces.go

@@ -57,5 +57,7 @@ func validateInterfaceF(command *cobra.Command, args []string) error {
 		os.Exit(1)
 	}
 
+	fmt.Printf("%s is a valid Astarte Interface\n", interfacePath)
+
 	return nil
 }

cmd/utils/triggers.go

@@ -57,5 +57,7 @@ func validateTriggerF(command *cobra.Command, args []string) error {
 		os.Exit(1)
 	}
 
+	fmt.Printf("%s is a valid Astarte Trigger\n", triggerPath)
+
 	return nil
 }