in src/main/scala/com/gu/fastly/api/FastlyApiClient.scala [185:189]
def statsWithFieldFilter(from: DateTime, to: DateTime, by: By.Value, region: Region.Value = Region.all, field: String): Future[Response] = {
val apiUrl = s"$fastlyApiUrl/stats/field/$field"
val params = statsParams(from, to, by, region)
AsyncHttpExecutor.execute(apiUrl, headers = commonHeaders, parameters = params)
}