`documentation` method does not print version on some resources where it should

[eeasley-coursera]

We have a resource like

@Singleton
class EnterpriseVoucherResource @Inject() (
    manager: EnterpriseVoucherManager,
    siteAuths: SiteAuths,
    superuserAuths: SuperuserAuths)
    (implicit ec: ExecutionContext)
  extends CourierCollectionResource[EnterpriseVoucherId, EnterpriseVoucher] {

  override def resourceName = "enterpriseVouchers"
  override def resourceVersion = 1
}

When printing out the documentation for this resource, I'd expect the paths to look like enterpriseVouchers.v1/$id. Instead, they look like enterpriseVouchers/$id.

It looks like it must be hitting this branch:
https://github.com/coursera/naptime/blob/master/naptime/src/main/scala/org/coursera/naptime/router2/NaptimePlayRouter.scala#L164

Original conversation at: https://coursera.slack.com/archives/dragon/p1484855939000114