Returns the field definitions needed to render a form for creating or editing an expense record of the given expenseType. The shape of fields varies by type (ReceiptVerification, CarSpecification, SubsistenceAllowance, FoodBenefitsSpecification, FuelBenefitsSpecification) — for example, ReceiptVerification surfaces amount and receipt-attachment fields, CarSpecification surfaces distance and route fields, and SubsistenceAllowance surfaces day-by-day per-diem fields. Initial values can be seeded from an existing expense record (pass expenseRecordId), from a card transaction (pass cardTransactionId), or from a business-trip / fuel-benefit context (pass fromFuelBenefit=true together with either businessTripId or fuelBenefitId); omit all of those to start from a blank record.