Function: register_credit_card
This tool belongs to the travel system, which allows users to book flights, manage credit cards, and view budget information. Tool description: Register a credit card
Parameters: access_token: type: string
description: The access token obtained from the authenticate method
card_number: type: string
description: The credit card number
expiration_date: type: string
description: The expiration date of the credit card in the format MM/YYYY
cardholder_name: type: string
description: The name of the cardholder
card_verification_number: type: integer
description: The card verification number
Required parameters: access_token, card_number, expiration_date, cardholder_name, card_verification_number
Response: card_id: type: string
description: The ID of the registered credit card