final void contentLength(long contentLength) {
        checkArgument(contentLength >= 0, "contentLength: %s (expected: >= 0)", contentLength);
        cache.put(HttpHeaderNames.CONTENT_LENGTH, contentLength);
        contentLengthMayBeUnknown = false;
        final String contentLengthString = StringUtil.toString(contentLength);
        setWithoutNotifying(HttpHeaderNames.CONTENT_LENGTH, contentLengthString);
    }
Adds the specified {@code setCookies} with {@link HttpHeaderNames#SET_COOKIE}.
core/src/main/java/com/linecorp/armeria/common/HttpHeadersBase.java