fix: delivery trip driver is only required on submit

[blaggacao]

This allows drafting trips and stops without yet deciding on the
assignable driver which, in real life, may well be decided on after
preparing and planning the trip.

[blaggacao]

Something seems to be flaky with this test. In the previous run it was Reserved != Delivered, now it's Partially Delivered != Delivered. I have no knowledge of what makes this test proven flaky and whether this PR surfaces it (and if so: how?) ...

======================================================================
 FAIL  test_stock_reservation_against_sales_order (erpnext.selling.doctype.sales_order.test_sales_order.TestSalesOrder.test_stock_reservation_against_sales_order)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/opt/hostedtoolcache/Python/3.11.4/x64/lib/python3.11/contextlib.py", line 81, in inner
    return func(*args, **kwds)
           ^^^^^^^^^^^^^^^^^^^
    args = (<erpnext.selling.doctype.sales_order.test_sales_order.TestSalesOrder testMethod=test_stock_reservation_against_sales_order>,)
    func = <function TestSalesOrder.test_stock_reservation_against_sales_order at 0x7f243fe756c0>
    kwds = {}
    self = <contextlib._GeneratorContextManager object at 0x7f244050bdd0>
  File "/home/runner/frappe-bench/apps/erpnext/erpnext/selling/doctype/sales_order/test_sales_order.py", line 1912, in test_stock_reservation_against_sales_order
    self.assertEqual(sre_detail.status, "Delivered")
    cancel_stock_reservation_entries = <function cancel_stock_reservation_entries at 0x7f2442d7cae0>
    create_items = <function create_items at 0x7f243fa05c60>
    create_material_receipt = <function create_material_receipt at 0x7f243fa84360>
    dn1 = <DeliveryNote: MAT-DN-2023-00017 docstatus=1>
    dn2 = <DeliveryNote: MAT-DN-2023-00018 docstatus=1>
    get_sre_reserved_qty_details_for_voucher = <function get_sre_reserved_qty_details_for_voucher at 0x7f2442d7c720>
    get_stock_reservation_entries_for_voucher = <function get_stock_reservation_entries_for_voucher at 0x7f2442d7c540>
    has_reserved_stock = <function has_reserved_stock at 0x7f2442d7c860>
    item = <SalesOrderItem: 8df442e336 docstatus=1 parent=SAL-ORD-2023-00054>
    item_code = 'SR Batch and Serial Item 1'
    item_list = [{'item_code': 'SR Item 1', 'warehouse': '_Test Warehouse - _TC', 'qty': 17.0, 'uom': 'Nos', 'rate': 21, 'doctype': 'Sales Order Item'}, {'item_code': 'SR Item 2', 'warehouse': '_Test Warehouse - _TC', 'qty': 46.54, 'uom': 'Kg', 'rate': 68, 'doctype': 'Sales Order Item'}, {'item_code': 'SR Batch Item 1', 'warehouse': '_Test Warehouse - _TC', 'qty': 58.0, 'uom': 'Nos', 'rate': 111, 'doctype': 'Sales Order Item'}, {'item_code': 'SR Batch Item 2', 'warehouse': '_Test Warehouse - _TC', 'qty': 90.127, 'uom': 'Kg', 'rate': 20, 'doctype': 'Sales Order Item'}, {'item_code': 'SR Serial Item 1', 'warehouse': '_Test Warehouse - _TC', 'qty': 84.0, 'uom': 'Nos', 'rate': 117, 'doctype': 'Sales Order Item'}, {'item_code': 'SR Batch and Serial Item 1', 'warehouse': '_Test Warehouse - _TC', 'qty': 98.0, 'uom': 'Nos', 'rate': 56, 'doctype': 'Sales Order Item'}]
    items_details = {'SR Item 1': <Item: SR Item 1>, 'SR Item 2': <Item: SR Item 2>, 'SR Batch Item 1': <Item: SR Batch Item 1>, 'SR Batch Item 2': <Item: SR Batch Item 2>, 'SR Serial Item 1': <Item: SR Serial Item 1>, 'SR Batch and Serial Item 1': <Item: SR Batch and Serial Item 1>}
    properties = <Item: SR Batch and Serial Item 1>
    randint = <bound method Random.randint of <random.Random object at 0x5631698d9c40>>
    reserved_qty = 98.0
    reserved_qty_details = {'4c908125b1': 17.0, '5c1a9bd7d9': 90.127, '631d625a0f': 46.54, '752ad9a5ec': 98.0, '8d20bb9b63': 58.0, 'bb6c07cf84': 84.0}
    se = <StockEntry: MAT-STE-2023-00018 docstatus=2>
    self = <erpnext.selling.doctype.sales_order.test_sales_order.TestSalesOrder testMethod=test_stock_reservation_against_sales_order>
    so = <SalesOrder: SAL-ORD-2023-00054 docstatus=1>
    sre_detail = {'status': 'Partially Delivered', 'reserved_qty': 46.54, 'delivered_qty': 46.54}
    sre_details = [{'status': 'Partially Delivered', 'reserved_qty': 46.54, 'delivered_qty': 46.54}]
    stock_uom = 'Nos'
    uniform = <bound method Random.uniform of <random.Random object at 0x5631698d9c40>>
    warehouse = '_Test Warehouse - _TC'
AssertionError: 'Partially Delivered' != 'Delivered'
- Partially Delivered
+ Delivered

[codecov]

Codecov Report

Merging #35876 (5ea4c47) into develop (a90fe25) will decrease coverage by 0.01%.
The diff coverage is 50.00%.

❗ Current head 5ea4c47 differs from pull request most recent head 85155d5. Consider uploading reports for the commit 85155d5 to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #35876      +/-   ##
===========================================
- Coverage    64.20%   64.20%   -0.01%     
===========================================
  Files          811      811              
  Lines        62142    62144       +2     
===========================================
  Hits         39901    39901              
- Misses       22241    22243       +2     

Impacted Files	Coverage Δ
...pnext/stock/doctype/delivery_trip/delivery_trip.py	62.08% <50.00%> (-0.14%)	⬇️

... and 1 file with indirect coverage changes