Fix total return computing (#13)

Author: adborbas

Sources/Grodt/DTOs/DTOMappers/InvestmentDTOMapper.swift

@@ -89,10 +89,7 @@ class InvestmentDTOMapper {
     }
 
     private func calculateTotalReturn(profit: Decimal, cost: Decimal) -> Decimal {
-        guard cost != 0 else { return 0 }
-        var totalReturn = profit / cost
-        var roundedReturn = Decimal()
-        NSDecimalRound(&roundedReturn, &totalReturn, 2, .bankers)
-        return roundedReturn
+        guard cost > 0 else { return 0 }
+        return (profit / cost).rounded(to: 2)
     }
 }

Sources/Grodt/DTOs/DTOMappers/PortfolioDTOMapper.swift

@@ -93,7 +93,7 @@ actor Financials {
     }
 }
 
-fileprivate extension Decimal {
+extension Decimal {
     func rounded(to scale: Int, roundingMode: NSDecimalNumber.RoundingMode = .bankers) -> Decimal {
         var value = self
         var result = Decimal()