Account information of each customer.

Account activation is enabled/disabled by configuration.activation. Passing some days without activation, it would be better to delete the record.

Column	Type	Constraint	Description
shop	TEXT	PRIMARY KEY	Shop ID. (shop.username)
id	INTEGER		Identifier. (1-origin)
mail	TEXT	NOT NULL	Mail address and login name. Basically, unchangeable.
password	TEXT	NOT NULL	Password for login. Encrypted by String#crypt. Salt is declared by src/config.rb#CRYPTION_SALT. Of course, the salt must not be changed.
session_id	TEXT	UNIQUE	The session_id is for checking whether the user is logged in to the account.
fname	TEXT	NOT NULL	First name.
lname	TEXT	NOT NULL	Last name.
fname_kana	TEXT		Optional. Furigana of first name. (Japanese specific)
lname_kana	TEXT		Optional. Furigana of last name. (Japanese specific)
lang	TEXT	NOT NULL	Language of showing the shopping page and sending a mail. Default value is the language which a customer used when registration.
screenname	TEXT		Optional. Name to show for other customers (e.g. reviewer name).
birthday	DATE		Optional.
gender	INTEGER		Optional. 0:female 1:male
reg_date	DATE	NOT NULL	Registered date.
activate	TEXT		For account activation. If the value is NULL, the account is already activated. Otherwise, the value is randomized string to certify the activation.

CREATE TABLE account (
shop           TEXT,
id             INTEGER,
mail           TEXT     NOT NULL,
password       TEXT     NOT NULL,
session_id     TEXT     UNIQUE,
fname          TEXT     NOT NULL,
lname          TEXT     NOT NULL,
fname_kana     TEXT,
lname_kana     TEXT,
lang           TEXT     NOT NULL,
screenname     TEXT,
birthday       DATE,
gender         INTEGER,
reg_date       DATE     NOT NULL,
activate       TEXT,
PRIMARY KEY (shop, id));