Force make deposit only in the order

Its better to let the deposit line items be the only items in the order and prevent add new line items types to the cart or order.

Use case:

when you let users use buying from their balance and buy from other payment gateways, the user may deposit account and not complete the checkout operation, the decided to buy using other payment gateways and checkout, the user see incorrect balance computation and misconception.

Also it leads to wrong account increase as it increases the balance with the total amount instead of only increase the amount of deposit line item types only

Current solution:

1- prevent other payment gateways except in deposit.
2- delete deposit line item types if their exist other types.