static <T> T mergeInStroomDefaults(final T vanillaConfig,
                                       final T stroomDefaultConfig,
                                       final T actualConfig) {
        return mergeInStroomDefaults("", vanillaConfig, stroomDefaultConfig, actualConfig);
    }
@return The prefix for the user agent name
stroom-dropwizard-common/src/main/java/stroom/dropwizard/common/AbstractJerseyClientFactory.java