Testing HTTP PATCH using MockWebServer.
Since the standard JDK HTTP library does not support HTTP PATCH
by default, Spring must be able to locate a ClientHttpRequestFactory that does support HTTP PATCH.
Spring autoconfigures it's RestTemplateBuilder, and if either HttpComponentsClientHttpRequestFactory
or OkHttp3ClientHttpRequestFactory are found, they will be used, and they do provided the necessary support
for HTTP PATCH.
Since MockWebServer has a dependency on OkHttp, the tests runs fine since OkHttp puts
the OkHttp3ClientHttpRequestFactory on the test classpath.
Run ./gradlew clean build in order to execute the test.