Stores temporal credit card information while a customer is making a order. When order is made, it is moved to credit_card.

Column	Type	Constraint	Description
shop	TEXT	PRIMARY KEY	Shop ID (shop.username).
session	TEXT		Login session ID (session.login_session).
company	TEXT	NOT NULL	Credit card company.
number	TEXT	NOT NULL	Credit card number.
nominee	TEXT	NOT NULL	Credit card nominee. (Ascii roman character)
expiry_month	INTEGER	NOT NULL	Expiry date (month)
expiry_year	INTEGER	NOT NULL	Expiry date (year)
pin	TEXT	NOT NULL	Credit card pin number.
ip	TEXT	NOT NULL	IP address of ordered user. FIXME: This field must be moved to order.
billing_address_index	INTEGER		This field may use to certify whether the billing address is same as credit card owner's address. (destination.index) FIXME: Because of destination's content can be changed, it requires another table to just store the stable billing address. FIXME?: Another table to hold just a billing address may be needed.

CREATE TABLE session_credit(
shop                   TEXT,
session                TEXT,
company                TEXT      NOT NULL,
number                 TEXT      NOT NULL,
nominee                TEXT      NOT NULL,
expiry_month           INTEGER   NOT NULL,
expiry_year            INTEGER   NOT NULL,
pin                    TEXT      NOT NULL,
ip                     TEXT      NOT NULL,
billing_address_index  INTEGER,
PRIMARY KEY(shop, session)
);