code: public static function embedCampaigns(
          $html,
          $campaign = [],
          $additionalCampaigns = []
      ) {
          $pattern = '/<a(\s[^>]*)href="([^"]*)"([^>]*)>/si';
  
          $html = preg_replace_callback($pattern, function($matches) use ($campaign, $additionalCampaigns) {
              $href = GoogleCampaignPlugin::replaceLink($matches[2], $campaign, $additionalCampaigns);
              return "<a{$matches[1]}href=\"{$href}\"{$matches[3]}>";
          }, $html);
  
          return $html;
      }
docs: Embed campaigns into the newsletter and return the updated html
  
  @param  string $html                 the email content
  @param  array  $campaign             the general campaign for the newsletter
  @param  array  $additionalCampaigns  additional campaigns to be replaced
  @return string $html                 html with updated hrefs