Invoice Sales Timesheets with a Date Limit

This module lets you cap which timesheets are taken into account when invoicing a service sold by the hour.

• On a sales order you get a new field, timesheet_limit_date (Timesheet Limit Date), shown on the order form right after the payment terms. Its help text says the invoice will be created with timesheets up to and including that date.
• The same field is added to customer invoices, on the invoice form after the payment terms.
• When the sales order is invoiced, the limit date is carried over to the invoice, and the date on the sales order is then cleared.
• While a limit date is set on the order, the delivered quantity of timesheet-based lines is computed only from timesheet entries dated on or before that date, and the timesheet list shown on the order is filtered the same way.
• On a draft customer invoice that has a limit date, any timesheet line linked to that invoice but dated after the limit date is detached from the invoice, so it is not billed there.

It touches sale.order, sale.order.line, account.invoice and account.invoice.line, and relies on the standard timesheet invoicing features of sale_timesheet.