if providing muliple values to listUsersByAccountInfo, like email and phone, or email and social provider info, and if doUnionOfAccountInfo is true, then it will list users that have all the provided info, whereas if doUnionOfAccountInfo is false, it will list users that have at least one of the provided info. For verifyEmailUsingToken, if attemptAccountLinking is true, it will attempt to link the account associated with the token to anu primary user with the same email. If there is no primary user with the same email, it will make the account itself a primary user (so future accounts can be linked to it). Else if attemptAccountLinking is false, it will not attempt any sort of account linking with the account associated with the token.