in src/main/scala/com/gu/fastly/api/FastlyApiClient.scala [143:146]
def vclSetAsMain(version: Int, name: String): Future[Response] = {
val apiUrl = s"$fastlyApiUrl/service/$serviceId/version/$version/vcl/$name/main"
AsyncHttpExecutor.execute(apiUrl, PUT, headers = commonHeaders)
}