Prevent adding recipe ingredients with a unit for which no conversion exists (closes #2013)

Wasn't a problem of the web frontend, only possible by externally/manually using the API and not thinking about that that's bullshit.

migrations/0202.sql

@@ -0,0 +1,25 @@
+DROP TRIGGER recipes_pos_qu_id_default;
+CREATE TRIGGER recipes_pos_qu_id_default AFTER INSERT ON recipes_pos
+BEGIN
+	UPDATE recipes_pos
+	SET qu_id = (SELECT qu_id_stock FROM products where id = product_id)
+	WHERE id = NEW.id
+		AND IFNULL(qu_id, '') = '';
+
+	SELECT CASE WHEN((
+		SELECT 1
+		FROM recipes_pos rp
+		JOIN quantity_unit_conversions_resolved qucr
+			ON qucr.product_id = rp.product_id
+			AND qucr.to_qu_id = rp.qu_id
+		WHERE rp.id = NEW.id
+
+		UNION
+
+		-- only_check_single_unit_in_stock = 1 ingredients can have any QU
+		SELECT 1
+		FROM recipes_pos rp
+		WHERE rp.id = NEW.id
+			AND IFNULL(rp.only_check_single_unit_in_stock, 0) = 1
+	) ISNULL) THEN RAISE(ABORT, "Provided qu_id doesn't have a related conversion for that product") END;
+END;