Changed

• Upgrade to OkHttp 4.12 (from 3.14).

  This is the version of OkHttp that is written in Kotlin, and as a result Retrofit now has a transitive Kotlin dependency. However, this is also the supported version of OkHttp whereas the previous version was out of support for nearly 4 years.

Note: The 3.x versions of Retrofit maintain forward binary-compatibility with the 2.x versions. This means libraries compiled against 2.x can still be used with the 3.x versions.