In 3.0.19 we had an @Override of the ResteasyClientBuilder#build() method. This already convoluted workaround was necessary to configure Apache HTTP client, for example, to add a request interceptor.
Such configuration is now effectively impossible after this commit:
The new build() method uses private fields, so it can't be duplicated. The HttpClientBuilder43.initDefaultEngine43() call is protected static. The ResteasyClient constructor is package visible. Code that was already bad is now much worse.