public ExportGroupBuilder responseHeader(CharSequence headerName) {
        requireNonNull(headerName, "headerName");
        final AsciiString key = toHeaderName(headerName);
        resHeaders.add(new ExportEntry<>(key, PREFIX_RES_HEADERS + key));
        return this;
    }
Adds the specified HTTP response header name to the export list.
core/src/main/java/com/linecorp/armeria/common/logging/ExportGroupBuilder.java