text: /* Create statements for the invoice db for SQLite */
  CREATE TABLE "biller" (
  	`id`	TEXT NOT NULL UNIQUE,
  	`name`	TEXT,
  	`street`	TEXT,
  	`postal`	TEXT,
  	`city`	TEXT,
  	`nation`	TEXT,
  	`tax_id`	TEXT,
  	PRIMARY KEY(id)
  );
  
  CREATE TABLE "banking" (
  	`id`	TEXT NOT NULL UNIQUE,
  	`biller_id`	TEXT,
  	`caption`	TEXT,
  	`institute`	TEXT,
  	`swift`	TEXT,
  	`iban`	TEXT,
  	PRIMARY KEY(id),
  	FOREIGN KEY(`biller_id`) REFERENCES biller ( id )
  );
  
  CREATE TABLE "customer" (
  	`id`	TEXT NOT NULL UNIQUE,
  	`name`	TEXT,
  	`street`	TEXT,
  	`postal`	TEXT,
  	`city`	TEXT,
  	`nation`	TEXT,
  	`tax_id`	TEXT,
  	`terms_amount`	INTEGER,
  	`terms_unit`	TEXT,
  	`valid_to`	TEXT,
  	PRIMARY KEY(id)
  );
  
  CREATE TABLE "item" (
  	`id`	TEXT NOT NULL UNIQUE,
  	`customer_id`	TEXT,
  	`caption`	TEXT,
  	`description`	TEXT,
  	`unit`	TEXT,
  	`unit_price`	REAL,
  	`currency`	TEXT,
  	`tax_percentage`	REAL,
  	`valid_to`	TEXT,
  	PRIMARY KEY(id),
  	FOREIGN KEY(`customer_id`) REFERENCES customer(id)
  );
  
  CREATE TABLE "invoice" (
  	`id`	TEXT NOT NULL UNIQUE,
  	`issue_date`	TEXT,
  	`biller_id`	TEXT,
  	`customer_id`	TEXT,
  	`delivery_date`	TEXT,
  	`periode_from`	TEXT,
  	`periode_to`	TEXT,
  	`currency`	TEXT,
  	`total_net`	REAL,
  	`total_tax`	REAL,
  	`total_gross`	REAL,
  	`export_date`	TEXT,
  	`due_date`	TEXT,
  	PRIMARY KEY(id),
  	FOREIGN KEY(`biller_id`) REFERENCES biller ( id ),
  	FOREIGN KEY(`customer_id`) REFERENCES customer ( id )
  );
  
  CREATE TABLE "invoice_item" (
  	`invoice_id`	TEXT,
  	`position`	INTEGER,
  	`description`	TEXT,
  	`unit`	TEXT,
  	`unit_price`	REAL,
  	`tax_percentage`	REAL,
  	`discount_percentage`	REAL,
  	`quantity`	REAL,
  	`price_net`	REAL,
  	FOREIGN KEY(`invoice_id`) REFERENCES invoice ( id )
  );
  
  CREATE TABLE "payment" (
  	`biller_id`	TEXT,
  	`invoice_id`	TEXT,
  	`customer_id`	TEXT,
  	`info`	TEXT,
  	`payment_date`	TEXT,
  	`amount`	REAL,
  	`currency`	TEXT
  );
  