Need to delete all orders from db associated to a diningsession

[Gabetn]

What

I.e. when we resolve that dining session in staff view by marking the bill as paid, we need to delete the orders from the database as opposed to removing them from the relationship to the diningsession and leaving them free floating.

Why

When displaying counter (notification) to staff of the number of orders we are counting this.props.orders.length which would require deletion of old free-floating orders.