Picture displayed in Twitter/Facebook cards when the link is posted to social networks. To be tested via https://cards-dev.twitter.com/validator and https://developers.facebook.com/tools/debug/
Only in case subscription to the newsletter via HTTP POST or GET methods. Put here data to be sent, using Python dictionary syntax. e.g.: <br> {'_wpcf7': 21,<br> '_wpcf7_version': '4.9',<br> '_wpcf7_locale': 'fr_FR',<br> '_wpcf7_unit_tag': 'wpcf7-f21-p5398-o1',<br> '_wpcf7_container_post': '5398',<br> 'your-email': ''<br> }
