add hr_timesheet_sheet_no_review, hr_timesheet_sheet_holidays, hr_timesheet_sheet_delete_cascade

hr_timesheet_sheet_delete_cascade/readme/USAGE.rst

@@ -0,0 +1,26 @@
+The native trash bin is removed from the sheet form, list and kanban views.
+Sheets are deleted from the **Delete Sheet** button in the header of the sheet
+form, or from the **Action** menu of the list view for several sheets at once.
+
+Both open a confirmation wizard that lists the sheets, the number of timesheet
+entries and the total number of hours that will be deleted, and a time off
+section that depends on the configured policy. Nothing is deleted until
+**Delete permanently** is pressed, and the button is hidden when something
+blocks the deletion.
+
+A plain ``sheet.unlink()`` from a script or a server action raises a
+``UserError`` that points to the button, so the confirmation step cannot be
+skipped by accident. Code that really means to delete does
+``sheet._with_delete_cascade().unlink()``.
+
+The cascade is armed by a sentinel object rather than by a plain value in the
+context, and ``_with_delete_cascade()`` is the only way to obtain it. The
+context of an RPC call is controlled by the caller, so a context flag holding
+a JSON value could be forged by any authenticated user and would delete a
+sheet without ever showing the confirmation; a sentinel compared by identity
+cannot be produced by a deserializer, and a method whose name starts with an
+underscore cannot be reached remotely.
+
+With the ``Cancel the time off`` policy, cancelling a time off request posts a
+message in its chatter telling the employee that the request has been refused.
+The wording talks about a refusal, not about a deleted timesheet sheet.