FIX: Do not check for duplicate links in Onebox (#13345)

If a user posted a URL that appeared inside a Onebox, then the user
got a duplicate link notice. This was fixed by skipping those links in
Ruby.

If a user posted a URL that was Oneboxes and contained other links that
appeared in previous posts, then the user got a duplicate link notice.
This was fixed by skipping those links in JavaScript.

app/assets/javascripts/discourse/app/controllers/composer.js

@@ -456,7 +456,7 @@ export default Controller.extend({
       $links.each((idx, l) => {
         const href = l.href;
         if (href && href.length) {
-          // skip links in quotes
+          // skip links in quotes and oneboxes
           for (let element = l; element; element = element.parentElement) {
             if (
               element.tagName === "DIV" &&
@@ -471,6 +471,14 @@ export default Controller.extend({
             ) {
               return true;
             }
+
+            if (
+              element.tagName === "ASIDE" &&
+              element.classList.contains("onebox") &&
+              href !== element.dataset["onebox-src"]
+            ) {
+              return true;
+            }
           }
 
           const [warn, info] = linkLookup.check(post, href);