Update Shipment Line Items

Updates the line items for a specific shipment. The request body must include the complete list of line items as returned by the GET /shipment/{shipmentId}:getLineItems endpoint — partial updates are not supported. Retrieve the current line items first, modify the desired fields, and submit the full payload. **Important:** The `is_manually_assigned_lot` field must be set to the same value for all line items in the request. When set to `true` on any item, ShipBob treats all lot assignments in the shipment as manually reviewed — ShipBob will not auto-assign or re-optimize lots for any item. When set to `false`, ShipBob manages lot selection automatically. Mixing `true` and `false` across items in the same request will result in a validation error. **Note on error handling:** This endpoint returns HTTP 200 for both successful and failed operations. Always check the `is_success` field in the response body to determine the outcome. When `is_success` is `false`, the `error` object contains the error code and message. HTTP 400 is only returned when the request body itself is missing or empty.