issue #22029 setup

TODO
  - resolve question: to what Receivable to attach a new CashReceipt for
    SalesOrder allocation? or contrive a new one for this purpose?
CashReceiptAllocation
  - links CashReceipt, CashReceiptLine, and a target Document to which
    part of the CashReceipt balance will be applied
  - added CashReceiptAllocation relations, lists, and a
    CashReceiptWidget
SalesOrder
  - extended SalesOrder ORM with allocations list
  - added Payment panel to Workspace