in src/main/scala/ZuoraService.scala [188:194]
def getInvoiceTransactionSummary(accountId: String): String \/ InvoiceTransactionSummary = {
logInfo(accountId, s"getting invoice transaction summary from Zuora")
val request = buildRequest(config, s"transactions/invoices/accounts/${accountId}").get().build()
val call = restClient.newCall(request)
val response = call.execute
convertResponseToCaseClass[InvoiceTransactionSummary](accountId, response)
}