there is this text: "@CreditCardNumber(ignoreNonDigitCharacters=)
Checks that the annotated character sequence passes the Luhn checksum test. Note, this validation aims to check for user mistakes, not credit card validity! See also Anatomy of Credit Card Numbers. ignoreNonDigitCharacters allows to ignore non digit characters. The default is false."
That link "Anatomy of Credit Card Numbers" leads to a "domain name for sale" website.