private void export(State state, RequestLog log) {
        exportBuiltIns(state, log);
        exportAttributes(state);
        exportRequestHeaders(state, log);
        exportResponseHeaders(state, log);
    }
Returns a {@link Map} whose key is an export key set through {@code add*()} in
{@link RequestContextExporterBuilder} and value is extracted from the specified {@link RequestContext}.
core/src/main/java/com/linecorp/armeria/common/logging/RequestContextExporter.java