Handles the sending of a One-Time Password (OTP) to a customer for redemption purposes within a merchant's loyalty program. It retrieves the associated merchant from the tracking ID. Then, it attempts to fetch the user associated with the request. If no valid user is found, it returns an error indicating an invalid customer phone number. If a valid user is found, it proceeds to generate and send the OTP to the user via SMS. If the OTP sending is successful, the controller method returns a success response indicating that the OTP has been sent. If the user is not found, it returns an error indicating that the user was not found.