Fixed that "Spoil rate" and "Average shelf life" on the product card was wrong in most cases

migrations/0090.sql

@@ -0,0 +1,17 @@
+DROP VIEW stock_average_product_shelf_life;
+CREATE VIEW stock_average_product_shelf_life
+AS
+SELECT
+	p.id,
+	CASE WHEN x.product_id IS NULL THEN -1 ELSE AVG(x.shelf_life_days) END AS average_shelf_life_days
+FROM products p
+LEFT JOIN (
+		SELECT
+			sl_p.product_id,
+			JULIANDAY(sl_p.best_before_date) - JULIANDAY(sl_p.purchased_date) AS shelf_life_days
+		FROM stock_log sl_p
+		WHERE sl_p.transaction_type = 'purchase'
+			AND sl_p.undone = 0
+	) x
+	ON p.id = x.product_id
+GROUP BY p.id;