@Nullable
    default Boolean defaultUseHttp1Pipelining() {
        return null;
    }
Returns the default value of the {@link ClientFactoryBuilder#useHttp1Pipelining(boolean)} option.
Note that this flag has no effect if a user specified the value explicitly via
{@link ClientFactoryBuilder#useHttp1Pipelining(boolean)}.

<p>This flag is disabled by default. Specify the
{@code -Dcom.linecorp.armeria.defaultUseHttp1Pipelining=true} JVM option to enable it.
core/src/main/java/com/linecorp/armeria/common/FlagsProvider.java