FIX: Use username for nested quotes (#16523)

There was an edge when a user re-quoted a nested quote that it would return an incorrect `full name` but the correct `username` for the original quote. This PR updates the logic to fall back to using the OP user's username. 

The complexity of the changes required to allow for full names to be displayed on nested quotes far outweighs how rare quoting nested quotes is.

app/assets/javascripts/discourse/app/lib/quote.js

@@ -9,10 +9,15 @@ export function buildQuote(post, contents, opts = {}) {
     return "";
   }
 
-  const name = prioritizeNameFallback(
-    post.name,
-    opts.username || post.username
-  );
+  let fullName = post.name;
+  // if the quote username data attr is present but it does not
+  // match the post username then fallback to the quote username instead of fetching
+  // the full name from the post
+  if (opts.username && opts.username !== post.username) {
+    fullName = null;
+  }
+
+  const name = prioritizeNameFallback(fullName, opts.username || post.username);
 
   const params = [
     name,
@@ -26,7 +31,7 @@ export function buildQuote(post, contents, opts = {}) {
   if (
     helperContext().siteSettings.display_name_on_posts &&
     !helperContext().siteSettings.prioritize_username_in_ux &&
-    post.name
+    fullName
   ) {
     params.push(`username:${opts.username || post.username}`);
   }

app/assets/javascripts/discourse/tests/acceptance/composer-actions-test.js

@@ -611,6 +611,16 @@ acceptance("Prioritize Full Name", function (needs) {
       '[quote="james, john, the third, post:2, topic:54079, full:true, username:james_john"]\nThis is a short topic.\n[/quote]'
     );
   });
+
+  test("Quoting a nested quote returns the correct username", async function (assert) {
+    await visit("/t/short-topic-with-two-posts/54079");
+    await selectText("#post_4 p");
+    await click(".insert-quote");
+    assert.strictEqual(
+      queryAll(".d-editor-input").val().trim(),
+      '[quote="james_john, post:2, topic:54079"]\nThis is a short topic.\n[/quote]'
+    );
+  });
 });
 
 acceptance("Prioritizing Name fall back", function (needs) {

app/assets/javascripts/discourse/tests/fixtures/topic.js

@@ -6449,7 +6449,7 @@ export default {
           id: 398,
           name: "james, john, the third",
           username: "james_john",
-          avatar_template: "/images/avatar.png",
+          avatar_template: "/letter_avatar_proxy/v4/letter/j/3be4f8/{size}.png",
           uploaded_avatar_id: 5697,
           created_at: "2013-02-05T21:29:00.280Z",
           cooked: "<p>This is a short topic.</p>",
@@ -6500,7 +6500,7 @@ export default {
           id: 410,
           name: "james, john, the third",
           username: "james_john",
-          avatar_template: "/images/avatar.png",
+          avatar_template: "/letter_avatar_proxy/v4/letter/j/3be4f8/{size}.png",
           uploaded_avatar_id: 5697,
           created_at: "2013-02-05T21:29:00.280Z",
           cooked: "<p>This is a short topic.</p>",
@@ -6551,7 +6551,7 @@ export default {
           id: 419,
           name: "Tim Stone",
           username: "tms",
-          avatar_template: "/images/avatar.png",
+          avatar_template: "/letter_avatar_proxy/v4/letter/t/3be4f8/{size}.png",
           uploaded_avatar_id: 40181,
           created_at: "2013-02-05T21:32:47.649Z",
           cooked: "<p>Yeah it is a short one</p>",
@@ -6598,6 +6598,58 @@ export default {
           can_view_edit_history: true,
           wiki: false,
         },
+        {
+          id: 421,
+          name: "Tim Stone",
+          username: "tms",
+          avatar_template: "/letter_avatar_proxy/v4/letter/t/3be4f8/{size}.png",
+          uploaded_avatar_id: 40181,
+          created_at: "2013-02-05T21:32:47.649Z",
+          cooked: "<p>Yeah it is a short one</p>",
+          cooked: '<aside class="quote no-group" data-username="james_john" data-post="2" data-topic="54079"><div class="title" style="cursor: pointer;"><div class="quote-controls"><span class="svg-icon-title" title="expand/collapse"><svg class="fa d-icon d-icon-chevron-down svg-icon svg-string" xmlns="http://www.w3.org/2000/svg"><use href="#chevron-down"></use></svg></span><a href="/t/hello-world-i-am-posting-an-image/158/1" title="go to the quoted post" class="back"><svg class="fa d-icon d-icon-arrow-up svg-icon svg-string" xmlns="http://www.w3.org/2000/svg"><use href="#arrow-up"></use></svg></a></div> <img alt="" width="20" height="20" src="/letter_avatar_proxy/v4/letter/j/3be4f8/90.png" class="avatar"> james_john:</div><blockquote><p>This is a short topic.</p></blockquote></aside><p>there is a quote above</p>',
+          post_number: 4,
+          post_type: 1,
+          updated_at: "2013-02-06T10:15:27.965Z",
+          like_count: 4,
+          reply_count: 0,
+          reply_to_post_number: null,
+          quote_count: 1,
+          incoming_link_count: 16,
+          reads: 460,
+          score: 308.35,
+          yours: false,
+          topic_id: 54079,
+          topic_slug: "short-topic-with-two-posts",
+          display_username: "Tim Stone",
+          primary_group_name: null,
+          version: 2,
+          can_edit: true,
+          can_delete: true,
+          can_recover: true,
+          link_counts: [],
+          read: true,
+          user_title: "Great contributor",
+          actions_summary: [
+            {
+              id: 2,
+              count: 4,
+              hidden: false,
+              can_act: true,
+            },
+          ],
+          moderator: false,
+          admin: false,
+          staff: false,
+          user_id: 9,
+          hidden: false,
+          hidden_reason_id: null,
+          trust_level: 2,
+          deleted_at: null,
+          user_deleted: false,
+          edit_reason: null,
+          can_view_edit_history: true,
+          wiki: false,
+        },
       ],
       stream: [398, 419],
       gaps: { before: {}, after: { 398: [419] } },