oembed: extract legacy allowfullscreen if it is missing in allow attribute

Author: iparamonau

plugins/links/oembed-rich.js

@@ -110,6 +110,10 @@ export default {
             widget.rel = widget.rel.concat(iframe.allow.replace(/autoplay;?\s?\*?/ig, '').split(/\s?\*?(?:;|,)\s?\*?/g));
         }
 
+        if (iframe && iframe.allowfullscreen === '' && widget.rel.indexOf('fullscreen') === -1) { // ex.: Supademo
+            widget.rel.push('fullscreen');
+        }        
+
         if (iframe && iframe.src && iframe.onmousewheel === '') {
             widget.rel.push('nowheel');
         }

plugins/links/oembed-video.js

@@ -66,6 +66,10 @@ export default {
             player.rel = player.rel.concat(iframe.allow.replace(/autoplay;?\s?\*?/ig, '').split(/\s?\*?(?:;|,)\s?\*?/g));
         }
 
+        if (iframe && iframe.allowfullscreen === '' && player.rel.indexOf('fullscreen') === -1) {
+            player.rel.push('fullscreen');
+        }
+
         if (player.href && whitelistRecord.isAllowed('oembed.video', "accept") && player.type === CONFIG.T.text_html) {
             player.accept = player.type;
             delete player.type;