async sendForHTMLResource(resource) {
        let links = resource.html ? this.getLinks(resource.html) : [];
        if (resource.previousHtml) {
            // Only send for NEW or DELETED links (to avoid spamming when lots of small changes happen to a post)
            const existingLinks = links;
            links = [];
            const oldLinks = this.getLinks(resource.previousHtml);

            for (const link of oldLinks) {
                if (!existingLinks.find(l => l.href === link.href)) {
                    // Deleted link
                    links.push(link);
                }
            }

            for (const link of existingLinks) {
                if (!oldLinks.find(l => l.href === link.href)) {
                    // New link
                    links.push(link);
                }
            }
        }

        if (links.length) {
            logging.info('[Webmention] Sending all webmentions for ' + resource.url.href);
        }

        await this.sendAll({
            url: resource.url,
            links
        });
    }
Send a webmention call for the links in a resource.
@param {object} resource
@param {URL} resource.url
@param {string} resource.html
@param {string|null} [resource.previousHtml]