}

        // Disallow instance fields. This doesn't guarantee that the object is immutable, just makes it less likely
        // We might tighten this constraint to also disallow any _code_ on immutable types that reaches out to static state
        for (Field field : type.getDeclaredFields()) {

OkHttp is **not** source-compatible for Kotlin callers, but upgrading should be automatic thanks to
Kotlin’s powerful deprecation features. Most developers should be able to use IntelliJ’s _Code
Cleanup_ for a safe and fast upgrade.


Backwards-Incompatible Changes
------------------------------

#### OkHttpClient final methods

  kube::release::package_client_tarballs &
  kube::release::package_kube_manifests_tarball &
  kube::util::wait-for-jobs || { kube::log::error "previous tarball phase failed"; return 1; }

  # _node and _server tarballs depend on _src tarball
  kube::release::package_node_tarballs &
  kube::release::package_server_tarballs &
  kube::util::wait-for-jobs || { kube::log::error "previous tarball phase failed"; return 1; }