when you call `contains(null)` on them!
 *  Fix: Retain binary-compatibility in `okhttp3.internal.HttpHeaders.hasBody()`. Some unscrupulous
    coders call this and we don't want their users to suffer.


## Version 4.0.0

_2019-06-26_

**This release upgrades OkHttp to Kotlin.** We tried our best to make fast and safe to upgrade

**This release introduces new Kotlin-friendly APIs.** When we migrated OkHttp from Java to Kotlin in
OkHttp 4.0, we kept our Java-first APIs. With 5.0 we're continuing to support Java and adding
additional improvements for Kotlin users. In this alpha we're excited to skip-the-builder for
requests and remove a common source of non-null assertions (`!!`) on the response body.