Reuse of verification codes should be disabled

[godwinpinto]

Feature
TOTP by nature allows you to use the code any no. of times since it is valid for 30 seconds. However, this will lead to risks and should be not usable once successfully verified.

Solution
Store code in hashed format in db post successful verification, store the 'n' times field in system and validate the if it is among them. Appropriate message should also be shown if it is among them to try after 'X' seconds.