Backdating: Outbound Shipment Picked Date

Overview

Allow users to set a historical picked date on a new outbound shipment via backdated_datetime. Stock allocation then uses historical stock-on-hand — stock that arrived after the backdated date is excluded from the allocation UI.

Design

Can only be set while the shipment is in New status (before any status progression).
Uses backdated_datetime on the invoice (the same field as prescriptions, so the backdating infrastructure is shared).
If any lines exist when backdating, they are deleted atomically in generate — the user is warned with a confirmation dialog on the frontend before the request is sent.
handle_new_backdated_datetime() sets backdated_datetime and replaces allocated_datetime / picked_datetime / verified_datetime with the backdated value (only if they were previously set).
Historical stock filtering: get_historical_stock_lines excludes stock lines with ≤ 0 historical availability.
Gated by the global Backdating preference.
Backdating.max_days limits how far back the date can be set. 0 means unlimited.
A stocktake warning is shown if a stocktake exists after the selected date.

Backend validation (server-side enforced)

From outbound_shipment/update/validate.rs:

Backdating.enabled must be true → CantBackDate("Backdating of shipments is not enabled")
Invoice must be in New status → CantBackDate("Can only backdate new outbound shipments")
backdated_datetime must not be in the future → CantBackDate("Cannot set date in the future")
If Backdating.max_days > 0, must not be before now - max_days → ExceedsMaximumBackdatingDays

Backend generate

When backdated_datetime is set (outbound_shipment/update/generate.rs):

handle_new_backdated_datetime() sets invoice.backdated_datetime and replaces allocated/picked/verified datetimes (when present) with the backdated value.
All existing invoice lines for this invoice are added to lines_to_trim and deleted in the transaction, and update_lines is cleared so nothing is re-inserted.

What works automatically

Stock allocation filtering — stock_out_line/insert/validate.rs already calls invoice_backdated_date() and uses get_historical_stock_line_available_quantity(), so any invoice with backdated_datetime set will only allocate stock that existed at that date.
Historical SOH display — get_draft_stock_out_lines() already passes backdated_datetime to get_historical_stock_lines(), so the allocation UI shows historical stock without further wiring.
Status datetime handling — once handle_new_backdated_datetime() replaces the status timestamps, downstream picked/shipped/verified transitions behave naturally.

Key files

Backend (Rust)

File	Change
`server/service/src/invoice/outbound_shipment/update/mod.rs`	`backdated_datetime: Option<DateTime<Utc>>` field on `UpdateOutboundShipment`; `CantBackDate(String)` and `ExceedsMaximumBackdatingDays` error variants
`server/service/src/invoice/outbound_shipment/update/validate.rs`	Validation: preference enabled, New status only, not in future, within `max_days`
`server/service/src/invoice/outbound_shipment/update/generate.rs`	Calls `handle_new_backdated_datetime()`; collects all existing lines into `lines_to_trim` so they are deleted atomically; clears `update_lines`
`server/service/src/invoice/invoice_date_utils.rs`	Shared `handle_new_backdated_datetime()`
`server/graphql/invoice/src/mutations/outbound_shipment/update.rs`	`backdatedDatetime: DateTime<Utc>` on the GraphQL input; error mapping

Frontend (TypeScript)

File	Change
`client/packages/invoices/src/OutboundShipment/DetailView/SidePanel/PickedDateInput.tsx`	Picked date picker in the Additional Info side panel; preference/status-dependent disabling; line-deletion confirmation; stocktake warning
`client/packages/invoices/src/OutboundShipment/api/api.ts`	`backdatedDatetime` passed via `toUpdate`
`client/packages/invoices/src/OutboundShipment/api/operations.graphql`	`backdatedDatetime` added to the `Outbound` fragment

User flow

Create a new outbound shipment (status = New).
If the Backdating preference is enabled, the Picked date field appears in the Additional Info side panel.
The date picker constrains to: not in the future, and not before max_days ago (when max_days > 0).
User picks a date in the past.
If lines already exist, a confirmation dialog warns they will be deleted.
If a stocktake exists on or after the chosen date, an additional warning is shown.
On confirm, the backend sets backdated_datetime, replaces status datetimes, and deletes any existing lines — all in the same transaction.
Allocation now shows only stock that existed at the picked date, with historical SOH values.