CalculatorService.scala

trait CalculatorService extends Service {

  def calculate(fromValue: BigDecimal,
                fromUnit: String,
                toUnit: String
               ): ServiceCall[NotUsed, CalculatedValue]

  def descriptor(): Descriptor =
    named("calculatorservice")
      .`with`(
        restCall(
            Method.GET, 
            "/api/calculator/exchange?fromValue&fromUnit&toUnit", 
            calculate _
        )
      )
      .`with`(classOf[BigDecimal], PathParamSerializers.BigDecimalSerializer)
      .`with`(new MicroserviceExceptionSerializer)
      .withAutoAcl(true)
}