Mail template data.

Column	Type	Constraint	Description
shop	TEXT	PRIMARY KEY	Shop ID. (shop.username)
id	INTEGER		Identifier.
name	TEXT	NOT NULL	Name of template. Because of it is just displaying to select on administration page, not multilingualized.
from	TEXT	NOT NULL	Mail address of sender.
reply_to	TEXT	NOT NULL	Mail address to reply.

CREATE TABLE mail_template(
shop     TEXT,
id       INTEGER,
name     TEXT    NOT NULL,
"from"   TEXT    NOT NULL,
reply_to TEXT    NOT NULL,
PRIMARY KEY(shop, id)
);

Multilingualized subject, header and footer of mail_template.

Column	Type	Constraint	Description
shop	TEXT	PRIMARY KEY	Shop ID. (shop.username)
template_id	INTEGER		Template ID. (mail_template.id)
lang	TEXT		Language key.
subject	TEXT	NOT NULL	Subject of mail.
header	TEXT	NOT NULL	Header part of body.
footer	TEXT	NOT NULL	Footer part of body above signature.

CREATE TABLE mail_template_content(
shop         TEXT,
template_id  INTEGER,
lang         TEXT,
subject      TEXT    NOT NULL,
header       TEXT    NOT NULL,
footer       TEXT    NOT NULL,
PRIMARY KEY(shop, template_id, lang)
);